Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

140 files changed, 16637 insertions, 0 deletions

diff --git a/dom/file/BaseBlobImpl.cpp b/dom/file/BaseBlobImpl.cpp
new file mode 100644
index 0000000000..5871b9da04
--- /dev/null
+++ b/dom/file/BaseBlobImpl.cpp
@@ -0,0 +1,75 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/BaseBlobImpl.h"
+#include "mozilla/dom/BindingDeclarations.h"
+#include "nsRFPService.h"
+#include "prtime.h"
+
+namespace mozilla::dom {
+
+void BaseBlobImpl::GetName(nsAString& aName) const {
+  MOZ_ASSERT(mIsFile, "Should only be called on files");
+  aName = mName;
+}
+
+void BaseBlobImpl::GetDOMPath(nsAString& aPath) const {
+  MOZ_ASSERT(mIsFile, "Should only be called on files");
+  aPath = mPath;
+}
+
+void BaseBlobImpl::SetDOMPath(const nsAString& aPath) {
+  MOZ_ASSERT(mIsFile, "Should only be called on files");
+  mPath = aPath;
+}
+
+void BaseBlobImpl::GetMozFullPath(nsAString& aFileName,
+                                  SystemCallerGuarantee /* unused */,
+                                  ErrorResult& aRv) {
+  MOZ_ASSERT(mIsFile, "Should only be called on files");
+
+  GetMozFullPathInternal(aFileName, aRv);
+}
+
+void BaseBlobImpl::GetMozFullPathInternal(nsAString& aFileName,
+                                          ErrorResult& aRv) {
+  if (!mIsFile) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return;
+  }
+
+  aFileName.Truncate();
+}
+
+void BaseBlobImpl::GetType(nsAString& aType) { aType = mContentType; }
+
+int64_t BaseBlobImpl::GetLastModified(ErrorResult& aRv) {
+  MOZ_ASSERT(mIsFile, "Should only be called on files");
+  return mLastModificationDate / PR_USEC_PER_MSEC;
+}
+
+int64_t BaseBlobImpl::GetFileId() const { return -1; }
+
+/* static */
+uint64_t BaseBlobImpl::NextSerialNumber() {
+  static Atomic<uint64_t> nextSerialNumber;
+  return nextSerialNumber++;
+}
+
+void BaseBlobImpl::SetLastModificationDatePrecisely(int64_t aDate) {
+  MOZ_ASSERT(mIsFile, "Should only be called on files");
+  mLastModificationDate = aDate;
+}
+
+void BaseBlobImpl::SetLastModificationDate(RTPCallerType aRTPCallerType,
+                                           int64_t aDate) {
+  return SetLastModificationDatePrecisely(
+      nsRFPService::ReduceTimePrecisionAsUSecs(aDate, 0, aRTPCallerType));
+  // mLastModificationDate is an absolute timestamp so we supply a zero
+  // context mix-in
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/BaseBlobImpl.h b/dom/file/BaseBlobImpl.h
new file mode 100644
index 0000000000..7265fc2104
--- /dev/null
+++ b/dom/file/BaseBlobImpl.h
@@ -0,0 +1,158 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_BaseBlobImpl_h
+#define mozilla_dom_BaseBlobImpl_h
+
+#include "nsIGlobalObject.h"
+#include "mozilla/dom/BlobImpl.h"
+#include "mozilla/ErrorResult.h"
+
+namespace mozilla::dom {
+
+class FileBlobImpl;
+
+class BaseBlobImpl : public BlobImpl {
+  friend class FileBlobImpl;
+
+ public:
+  // File constructor.
+  BaseBlobImpl(const nsAString& aName, const nsAString& aContentType,
+               uint64_t aLength, int64_t aLastModifiedDate)
+      : mIsFile(true),
+        mContentType(aContentType),
+        mName(aName),
+        mStart(0),
+        mLength(aLength),
+        mSerialNumber(NextSerialNumber()),
+        mLastModificationDate(aLastModifiedDate) {
+    // Ensure non-null mContentType by default
+    mContentType.SetIsVoid(false);
+  }
+
+  // Blob constructor without starting point.
+  BaseBlobImpl(const nsAString& aContentType, uint64_t aLength)
+      : mIsFile(false),
+        mContentType(aContentType),
+        mStart(0),
+        mLength(aLength),
+        mSerialNumber(NextSerialNumber()),
+        mLastModificationDate(0) {
+    // Ensure non-null mContentType by default
+    mContentType.SetIsVoid(false);
+  }
+
+  // Blob constructor with starting point.
+  BaseBlobImpl(const nsAString& aContentType, uint64_t aStart, uint64_t aLength)
+      : mIsFile(false),
+        mContentType(aContentType),
+        mStart(aStart),
+        mLength(aLength),
+        mSerialNumber(NextSerialNumber()),
+        mLastModificationDate(0) {
+    // Ensure non-null mContentType by default
+    mContentType.SetIsVoid(false);
+  }
+
+  void GetName(nsAString& aName) const override;
+
+  void GetDOMPath(nsAString& aPath) const override;
+
+  void SetDOMPath(const nsAString& aPath) override;
+
+  int64_t GetLastModified(ErrorResult& aRv) override;
+
+  void GetMozFullPath(nsAString& aFileName, SystemCallerGuarantee /* unused */,
+                      ErrorResult& aRv) override;
+
+  void GetMozFullPathInternal(nsAString& aFileName, ErrorResult& aRv) override;
+
+  uint64_t GetSize(ErrorResult& aRv) override { return mLength; }
+
+  void GetType(nsAString& aType) override;
+
+  size_t GetAllocationSize() const override { return 0; }
+
+  size_t GetAllocationSize(
+      FallibleTArray<BlobImpl*>& aVisitedBlobImpls) const override {
+    return GetAllocationSize();
+  }
+
+  uint64_t GetSerialNumber() const override { return mSerialNumber; }
+
+  already_AddRefed<BlobImpl> CreateSlice(uint64_t aStart, uint64_t aLength,
+                                         const nsAString& aContentType,
+                                         ErrorResult& aRv) const override {
+    return nullptr;
+  }
+
+  const nsTArray<RefPtr<BlobImpl>>* GetSubBlobImpls() const override {
+    return nullptr;
+  }
+
+  void CreateInputStream(nsIInputStream** aStream,
+                         ErrorResult& aRv) const override {
+    aRv.Throw(NS_ERROR_NOT_IMPLEMENTED);
+  }
+
+  int64_t GetFileId() const override;
+
+  void SetLazyData(const nsAString& aName, const nsAString& aContentType,
+                   uint64_t aLength, int64_t aLastModifiedDate) override {
+    mName = aName;
+    mContentType = aContentType;
+    mLength = aLength;
+    SetLastModificationDatePrecisely(aLastModifiedDate);
+    mIsFile = !aName.IsVoid();
+  }
+
+  bool IsMemoryFile() const override { return false; }
+
+  bool IsFile() const override { return mIsFile; }
+
+  void GetBlobImplType(nsAString& aBlobImplType) const override {
+    aBlobImplType = u"BaseBlobImpl"_ns;
+  }
+
+ protected:
+  ~BaseBlobImpl() override = default;
+
+  /**
+   * Returns a new, effectively-unique serial number. This should be used
+   * by implementations to obtain a serial number for GetSerialNumber().
+   * The implementation is thread safe.
+   */
+  static uint64_t NextSerialNumber();
+
+  void SetLastModificationDate(RTPCallerType aRTPCallerType, int64_t aDate);
+  void SetLastModificationDatePrecisely(int64_t aDate);
+
+#ifdef DEBUG
+  bool IsLastModificationDateUnset() const {
+    return mLastModificationDate == INT64_MAX;
+  }
+#endif
+
+  const nsString mBlobImplType;
+
+  bool mIsFile;
+
+  nsString mContentType;
+  nsString mName;
+  nsString mPath;  // The path relative to a directory chosen by the user
+
+  uint64_t mStart;
+  uint64_t mLength;
+
+  const uint64_t mSerialNumber;
+
+ private:
+  int64_t mLastModificationDate;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_BaseBlobImpl_h
diff --git a/dom/file/Blob.cpp b/dom/file/Blob.cpp
new file mode 100644
index 0000000000..bb21a1f117
--- /dev/null
+++ b/dom/file/Blob.cpp
@@ -0,0 +1,376 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "Blob.h"
+#include "EmptyBlobImpl.h"
+#include "File.h"
+#include "MemoryBlobImpl.h"
+#include "mozilla/dom/BlobBinding.h"
+#include "mozilla/dom/BodyStream.h"
+#include "mozilla/dom/ReadableStream.h"
+#include "mozilla/dom/WorkerCommon.h"
+#include "mozilla/dom/WorkerPrivate.h"
+#include "mozilla/HoldDropJSObjects.h"
+#include "MultipartBlobImpl.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsIGlobalObject.h"
+#include "nsIInputStream.h"
+#include "nsPIDOMWindow.h"
+#include "StreamBlobImpl.h"
+#include "StringBlobImpl.h"
+#include "js/GCAPI.h"
+
+namespace mozilla::dom {
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(Blob)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(Blob)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mGlobal)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_WEAK_REFERENCE
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(Blob)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mGlobal)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(Blob)
+  NS_IMPL_CYCLE_COLLECTION_TRACE_PRESERVED_WRAPPER
+NS_IMPL_CYCLE_COLLECTION_TRACE_END
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(Blob)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+  NS_INTERFACE_MAP_ENTRY_CONCRETE(Blob)
+  NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(Blob)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(Blob)
+
+void Blob::MakeValidBlobType(nsAString& aType) {
+  char16_t* iter = aType.BeginWriting();
+  char16_t* end = aType.EndWriting();
+
+  for (; iter != end; ++iter) {
+    char16_t c = *iter;
+    if (c < 0x20 || c > 0x7E) {
+      // Non-ASCII char, bail out.
+      aType.Truncate();
+      return;
+    }
+
+    if (c >= 'A' && c <= 'Z') {
+      *iter = c + ('a' - 'A');
+    }
+  }
+}
+
+/* static */
+Blob* Blob::Create(nsIGlobalObject* aGlobal, BlobImpl* aImpl) {
+  MOZ_ASSERT(aImpl);
+
+  MOZ_ASSERT(aGlobal);
+  if (NS_WARN_IF(!aGlobal)) {
+    return nullptr;
+  }
+
+  return aImpl->IsFile() ? new File(aGlobal, aImpl) : new Blob(aGlobal, aImpl);
+}
+
+/* static */
+already_AddRefed<Blob> Blob::CreateStringBlob(nsIGlobalObject* aGlobal,
+                                              const nsACString& aData,
+                                              const nsAString& aContentType) {
+  MOZ_ASSERT(aGlobal);
+  if (NS_WARN_IF(!aGlobal)) {
+    return nullptr;
+  }
+
+  RefPtr<BlobImpl> blobImpl = StringBlobImpl::Create(aData, aContentType);
+  RefPtr<Blob> blob = Blob::Create(aGlobal, blobImpl);
+  MOZ_ASSERT(!blob->mImpl->IsFile());
+  return blob.forget();
+}
+
+/* static */
+already_AddRefed<Blob> Blob::CreateMemoryBlob(nsIGlobalObject* aGlobal,
+                                              void* aMemoryBuffer,
+                                              uint64_t aLength,
+                                              const nsAString& aContentType) {
+  MOZ_ASSERT(aGlobal);
+  if (NS_WARN_IF(!aGlobal)) {
+    return nullptr;
+  }
+
+  RefPtr<Blob> blob = Blob::Create(
+      aGlobal, new MemoryBlobImpl(aMemoryBuffer, aLength, aContentType));
+  MOZ_ASSERT(!blob->mImpl->IsFile());
+  return blob.forget();
+}
+
+Blob::Blob(nsIGlobalObject* aGlobal, BlobImpl* aImpl)
+    : mImpl(aImpl), mGlobal(aGlobal) {
+  MOZ_ASSERT(mImpl);
+  MOZ_ASSERT(mGlobal);
+}
+
+Blob::~Blob() = default;
+
+bool Blob::IsFile() const { return mImpl->IsFile(); }
+
+const nsTArray<RefPtr<BlobImpl>>* Blob::GetSubBlobImpls() const {
+  return mImpl->GetSubBlobImpls();
+}
+
+already_AddRefed<File> Blob::ToFile() {
+  if (!mImpl->IsFile()) {
+    return nullptr;
+  }
+
+  RefPtr<File> file;
+  if (HasFileInterface()) {
+    file = static_cast<File*>(this);
+  } else {
+    file = new File(mGlobal, mImpl);
+  }
+
+  return file.forget();
+}
+
+already_AddRefed<File> Blob::ToFile(const nsAString& aName,
+                                    ErrorResult& aRv) const {
+  AutoTArray<RefPtr<BlobImpl>, 1> blobImpls({mImpl});
+
+  nsAutoString contentType;
+  mImpl->GetType(contentType);
+
+  RefPtr<MultipartBlobImpl> impl =
+      MultipartBlobImpl::Create(std::move(blobImpls), aName, contentType,
+                                mGlobal->GetRTPCallerType(), aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  RefPtr<File> file = new File(mGlobal, impl);
+  return file.forget();
+}
+
+already_AddRefed<Blob> Blob::CreateSlice(uint64_t aStart, uint64_t aLength,
+                                         const nsAString& aContentType,
+                                         ErrorResult& aRv) const {
+  RefPtr<BlobImpl> impl =
+      mImpl->CreateSlice(aStart, aLength, aContentType, aRv);
+  if (aRv.Failed()) {
+    return nullptr;
+  }
+
+  RefPtr<Blob> blob = Blob::Create(mGlobal, impl);
+  return blob.forget();
+}
+
+uint64_t Blob::GetSize(ErrorResult& aRv) { return mImpl->GetSize(aRv); }
+
+void Blob::GetType(nsAString& aType) { mImpl->GetType(aType); }
+
+void Blob::GetBlobImplType(nsAString& aBlobImplType) {
+  mImpl->GetBlobImplType(aBlobImplType);
+}
+
+already_AddRefed<Blob> Blob::Slice(const Optional<int64_t>& aStart,
+                                   const Optional<int64_t>& aEnd,
+                                   const Optional<nsAString>& aContentType,
+                                   ErrorResult& aRv) {
+  nsAutoString contentType;
+  if (aContentType.WasPassed()) {
+    contentType = aContentType.Value();
+  }
+
+  RefPtr<BlobImpl> impl = mImpl->Slice(aStart, aEnd, contentType, aRv);
+  if (aRv.Failed()) {
+    return nullptr;
+  }
+
+  RefPtr<Blob> blob = Blob::Create(mGlobal, impl);
+  return blob.forget();
+}
+
+size_t Blob::GetAllocationSize() const { return mImpl->GetAllocationSize(); }
+
+// contentTypeWithCharset can be set to the contentType or
+// contentType+charset based on what the spec says.
+// See: https://fetch.spec.whatwg.org/#concept-bodyinit-extract
+nsresult Blob::GetSendInfo(nsIInputStream** aBody, uint64_t* aContentLength,
+                           nsACString& aContentType,
+                           nsACString& aCharset) const {
+  return mImpl->GetSendInfo(aBody, aContentLength, aContentType, aCharset);
+}
+
+JSObject* Blob::WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto) {
+  return Blob_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+/* static */
+already_AddRefed<Blob> Blob::Constructor(
+    const GlobalObject& aGlobal, const Optional<Sequence<BlobPart>>& aData,
+    const BlobPropertyBag& aBag, ErrorResult& aRv) {
+  RefPtr<MultipartBlobImpl> impl = new MultipartBlobImpl();
+
+  nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(aGlobal.GetAsSupports());
+  MOZ_ASSERT(global);
+  if (aData.WasPassed()) {
+    nsAutoString type(aBag.mType);
+    MakeValidBlobType(type);
+    impl->InitializeBlob(aData.Value(), type,
+                         aBag.mEndings == EndingType::Native,
+                         global->GetRTPCallerType(), aRv);
+  } else {
+    impl->InitializeBlob(global->GetRTPCallerType(), aRv);
+  }
+
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  MOZ_ASSERT(!impl->IsFile());
+
+  RefPtr<Blob> blob = Blob::Create(global, impl);
+  return blob.forget();
+}
+
+int64_t Blob::GetFileId() const { return mImpl->GetFileId(); }
+
+bool Blob::IsMemoryFile() const { return mImpl->IsMemoryFile(); }
+
+void Blob::CreateInputStream(nsIInputStream** aStream, ErrorResult& aRv) const {
+  mImpl->CreateInputStream(aStream, aRv);
+}
+
+size_t BindingJSObjectMallocBytes(Blob* aBlob) {
+  MOZ_ASSERT(aBlob);
+
+  // TODO: The hazard analysis currently can't see that none of the
+  // implementations of the GetAllocationSize virtual method call can GC (see
+  // bug 1531951).
+  JS::AutoSuppressGCAnalysis nogc;
+
+  return aBlob->GetAllocationSize();
+}
+
+already_AddRefed<Promise> Blob::Text(ErrorResult& aRv) const {
+  return ConsumeBody(BodyConsumer::CONSUME_TEXT, aRv);
+}
+
+already_AddRefed<Promise> Blob::ArrayBuffer(ErrorResult& aRv) const {
+  return ConsumeBody(BodyConsumer::CONSUME_ARRAYBUFFER, aRv);
+}
+
+already_AddRefed<Promise> Blob::ConsumeBody(
+    BodyConsumer::ConsumeType aConsumeType, ErrorResult& aRv) const {
+  if (NS_WARN_IF(!mGlobal)) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIEventTarget> mainThreadEventTarget;
+  if (!NS_IsMainThread()) {
+    WorkerPrivate* workerPrivate = GetCurrentThreadWorkerPrivate();
+    MOZ_ASSERT(workerPrivate);
+    mainThreadEventTarget = workerPrivate->MainThreadEventTarget();
+  } else {
+    mainThreadEventTarget = mGlobal->EventTargetFor(TaskCategory::Other);
+  }
+
+  MOZ_ASSERT(mainThreadEventTarget);
+
+  nsCOMPtr<nsIInputStream> inputStream;
+  CreateInputStream(getter_AddRefs(inputStream), aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  return BodyConsumer::Create(mGlobal, mainThreadEventTarget, inputStream,
+                              nullptr, aConsumeType, VoidCString(),
+                              VoidString(), VoidCString(), VoidCString(),
+                              MutableBlobStorage::eOnlyInMemory, aRv);
+}
+
+namespace {
+
+class BlobBodyStreamHolder final : public BodyStreamHolder {
+ public:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_INHERITED(BlobBodyStreamHolder,
+                                                         BodyStreamHolder)
+
+  BlobBodyStreamHolder() { mozilla::HoldJSObjects(this); }
+
+  void NullifyStream() override { mozilla::DropJSObjects(this); }
+
+  void MarkAsRead() override {}
+
+  void SetReadableStreamBody(ReadableStream* aBody) override {
+    mStream = aBody;
+  }
+  ReadableStream* GetReadableStreamBody() override { return mStream; }
+
+ private:
+  RefPtr<ReadableStream> mStream;
+
+ protected:
+  ~BlobBodyStreamHolder() override { NullifyStream(); }
+};
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(BlobBodyStreamHolder)
+
+NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN_INHERITED(BlobBodyStreamHolder,
+                                               BodyStreamHolder)
+NS_IMPL_CYCLE_COLLECTION_TRACE_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(BlobBodyStreamHolder,
+                                                  BodyStreamHolder)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mStream)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(BlobBodyStreamHolder,
+                                                BodyStreamHolder)
+  tmp->NullifyStream();
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mStream)
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_ADDREF_INHERITED(BlobBodyStreamHolder, BodyStreamHolder)
+NS_IMPL_RELEASE_INHERITED(BlobBodyStreamHolder, BodyStreamHolder)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(BlobBodyStreamHolder)
+NS_INTERFACE_MAP_END_INHERITING(BodyStreamHolder)
+
+}  // anonymous namespace
+
+already_AddRefed<ReadableStream> Blob::Stream(JSContext* aCx,
+                                              ErrorResult& aRv) const {
+  nsCOMPtr<nsIInputStream> stream;
+  CreateInputStream(getter_AddRefs(stream), aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  if (NS_WARN_IF(!mGlobal)) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return nullptr;
+  }
+
+  RefPtr<BlobBodyStreamHolder> holder = new BlobBodyStreamHolder();
+
+  BodyStream::Create(aCx, holder, mGlobal, stream, aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  RefPtr<ReadableStream> rStream = holder->GetReadableStreamBody();
+  return rStream.forget();
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/Blob.h b/dom/file/Blob.h
new file mode 100644
index 0000000000..2314df32b3
--- /dev/null
+++ b/dom/file/Blob.h
@@ -0,0 +1,161 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_Blob_h
+#define mozilla_dom_Blob_h
+
+#include "mozilla/dom/BodyConsumer.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsCOMPtr.h"
+#include "nsWrapperCache.h"
+#include "nsWeakReference.h"
+
+class nsIGlobalObject;
+class nsIInputStream;
+
+namespace mozilla {
+class ErrorResult;
+
+namespace dom {
+
+struct BlobPropertyBag;
+class BlobImpl;
+class File;
+class GlobalObject;
+class OwningArrayBufferViewOrArrayBufferOrBlobOrUTF8String;
+class Promise;
+
+class ReadableStream;
+
+#define NS_DOM_BLOB_IID                              \
+  {                                                  \
+    0x648c2a83, 0xbdb1, 0x4a7d, {                    \
+      0xb5, 0x0a, 0xca, 0xcd, 0x92, 0x87, 0x45, 0xc2 \
+    }                                                \
+  }
+
+class Blob : public nsSupportsWeakReference, public nsWrapperCache {
+ public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS_FINAL
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(Blob)
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_DOM_BLOB_IID)
+
+  using BlobPart = OwningArrayBufferViewOrArrayBufferOrBlobOrUTF8String;
+
+  // This creates a Blob or a File based on the type of BlobImpl.
+  static Blob* Create(nsIGlobalObject* aGlobal, BlobImpl* aImpl);
+
+  static already_AddRefed<Blob> CreateStringBlob(nsIGlobalObject* aGlobal,
+                                                 const nsACString& aData,
+                                                 const nsAString& aContentType);
+
+  // The returned Blob takes ownership of aMemoryBuffer. aMemoryBuffer will be
+  // freed by free so it must be allocated by malloc or something
+  // compatible with it.
+  static already_AddRefed<Blob> CreateMemoryBlob(nsIGlobalObject* aGlobal,
+                                                 void* aMemoryBuffer,
+                                                 uint64_t aLength,
+                                                 const nsAString& aContentType);
+
+  BlobImpl* Impl() const { return mImpl; }
+
+  bool IsFile() const;
+
+  const nsTArray<RefPtr<BlobImpl>>* GetSubBlobImpls() const;
+
+  // This method returns null if this Blob is not a File; it returns
+  // the same object in case this Blob already implements the File interface;
+  // otherwise it returns a new File object with the same BlobImpl.
+  already_AddRefed<File> ToFile();
+
+  // This method creates a new File object with the given name and the same
+  // BlobImpl.
+  already_AddRefed<File> ToFile(const nsAString& aName, ErrorResult& aRv) const;
+
+  already_AddRefed<Blob> CreateSlice(uint64_t aStart, uint64_t aLength,
+                                     const nsAString& aContentType,
+                                     ErrorResult& aRv) const;
+
+  void CreateInputStream(nsIInputStream** aStream, ErrorResult& aRv) const;
+
+  int64_t GetFileId() const;
+
+  // A utility function that enforces the spec constraints on the type of a
+  // blob: no codepoints outside the ASCII range (otherwise type becomes empty)
+  // and lowercase ASCII only.  We can't just use our existing nsContentUtils
+  // ASCII-related helpers because we need the "outside ASCII range" check, and
+  // we can't use NS_IsAscii because its definition of "ASCII" (chars all <=
+  // 0x7E) differs from the file API definition (which excludes control chars).
+  static void MakeValidBlobType(nsAString& aType);
+
+  // WebIDL methods
+  nsIGlobalObject* GetParentObject() const { return mGlobal; }
+
+  bool IsMemoryFile() const;
+
+  // Blob constructor
+  static already_AddRefed<Blob> Constructor(
+      const GlobalObject& aGlobal, const Optional<Sequence<BlobPart>>& aData,
+      const BlobPropertyBag& aBag, ErrorResult& aRv);
+
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+  uint64_t GetSize(ErrorResult& aRv);
+
+  void GetType(nsAString& aType);
+
+  void GetBlobImplType(nsAString& aBlobImplType);
+
+  already_AddRefed<Blob> Slice(const Optional<int64_t>& aStart,
+                               const Optional<int64_t>& aEnd,
+                               const Optional<nsAString>& aContentType,
+                               ErrorResult& aRv);
+
+  size_t GetAllocationSize() const;
+
+  nsresult GetSendInfo(nsIInputStream** aBody, uint64_t* aContentLength,
+                       nsACString& aContentType, nsACString& aCharset) const;
+
+  already_AddRefed<ReadableStream> Stream(JSContext* aCx,
+                                          ErrorResult& aRv) const;
+  already_AddRefed<Promise> Text(ErrorResult& aRv) const;
+  already_AddRefed<Promise> ArrayBuffer(ErrorResult& aRv) const;
+
+ protected:
+  // File constructor should never be used directly. Use Blob::Create instead.
+  Blob(nsIGlobalObject* aGlobal, BlobImpl* aImpl);
+  virtual ~Blob();
+
+  virtual bool HasFileInterface() const { return false; }
+
+  already_AddRefed<Promise> ConsumeBody(BodyConsumer::ConsumeType aConsumeType,
+                                        ErrorResult& aRv) const;
+
+  // The member is the real backend implementation of this File/Blob.
+  // It's thread-safe and not CC-able and it's the only element that is moved
+  // between threads.
+  // Note: we should not store any other state in this class!
+  RefPtr<BlobImpl> mImpl;
+
+ private:
+  nsCOMPtr<nsIGlobalObject> mGlobal;
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(Blob, NS_DOM_BLOB_IID)
+
+// Override BindingJSObjectMallocBytes for blobs to tell the JS GC how much
+// memory is held live by the binding object.
+size_t BindingJSObjectMallocBytes(Blob* aBlob);
+
+}  // namespace dom
+}  // namespace mozilla
+
+inline nsISupports* ToSupports(mozilla::dom::Blob* aBlob) {
+  return static_cast<nsISupportsWeakReference*>(aBlob);
+}
+
+#endif  // mozilla_dom_Blob_h
diff --git a/dom/file/BlobImpl.cpp b/dom/file/BlobImpl.cpp
new file mode 100644
index 0000000000..fa31737c9d
--- /dev/null
+++ b/dom/file/BlobImpl.cpp
@@ -0,0 +1,99 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "BlobImpl.h"
+#include "File.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/ErrorResult.h"
+#include "nsIInputStream.h"
+
+namespace mozilla::dom {
+
+// Makes sure that aStart and aEnd is less then or equal to aSize and greater
+// than 0
+static void ParseSize(int64_t aSize, int64_t& aStart, int64_t& aEnd) {
+  CheckedInt64 newStartOffset = aStart;
+  if (aStart < -aSize) {
+    newStartOffset = 0;
+  } else if (aStart < 0) {
+    newStartOffset += aSize;
+  } else if (aStart > aSize) {
+    newStartOffset = aSize;
+  }
+
+  CheckedInt64 newEndOffset = aEnd;
+  if (aEnd < -aSize) {
+    newEndOffset = 0;
+  } else if (aEnd < 0) {
+    newEndOffset += aSize;
+  } else if (aEnd > aSize) {
+    newEndOffset = aSize;
+  }
+
+  if (!newStartOffset.isValid() || !newEndOffset.isValid() ||
+      newStartOffset.value() >= newEndOffset.value()) {
+    aStart = aEnd = 0;
+  } else {
+    aStart = newStartOffset.value();
+    aEnd = newEndOffset.value();
+  }
+}
+
+already_AddRefed<BlobImpl> BlobImpl::Slice(const Optional<int64_t>& aStart,
+                                           const Optional<int64_t>& aEnd,
+                                           const nsAString& aContentType,
+                                           ErrorResult& aRv) {
+  // Truncate aStart and aEnd so that we stay within this file.
+  uint64_t thisLength = GetSize(aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  int64_t start = aStart.WasPassed() ? aStart.Value() : 0;
+  int64_t end = aEnd.WasPassed() ? aEnd.Value() : (int64_t)thisLength;
+
+  ParseSize((int64_t)thisLength, start, end);
+
+  nsAutoString type(aContentType);
+  Blob::MakeValidBlobType(type);
+  return CreateSlice((uint64_t)start, (uint64_t)(end - start), type, aRv);
+}
+
+nsresult BlobImpl::GetSendInfo(nsIInputStream** aBody, uint64_t* aContentLength,
+                               nsACString& aContentType, nsACString& aCharset) {
+  MOZ_ASSERT(aContentLength);
+
+  ErrorResult rv;
+
+  nsCOMPtr<nsIInputStream> stream;
+  CreateInputStream(getter_AddRefs(stream), rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    return rv.StealNSResult();
+  }
+
+  *aContentLength = GetSize(rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    return rv.StealNSResult();
+  }
+
+  nsAutoString contentType;
+  GetType(contentType);
+
+  if (contentType.IsEmpty()) {
+    aContentType.SetIsVoid(true);
+  } else {
+    CopyUTF16toUTF8(contentType, aContentType);
+  }
+
+  aCharset.Truncate();
+
+  stream.forget(aBody);
+  return NS_OK;
+}
+
+NS_IMPL_ISUPPORTS(BlobImpl, BlobImpl)
+
+}  // namespace mozilla::dom
diff --git a/dom/file/BlobImpl.h b/dom/file/BlobImpl.h
new file mode 100644
index 0000000000..720c398cdd
--- /dev/null
+++ b/dom/file/BlobImpl.h
@@ -0,0 +1,114 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_BlobImpl_h
+#define mozilla_dom_BlobImpl_h
+
+#include "nsISupports.h"
+#include "nsString.h"
+
+#define BLOBIMPL_IID                                 \
+  {                                                  \
+    0xbccb3275, 0x6778, 0x4ac5, {                    \
+      0xaf, 0x03, 0x90, 0xed, 0x37, 0xad, 0xdf, 0x5d \
+    }                                                \
+  }
+
+class nsIInputStream;
+
+namespace mozilla {
+class ErrorResult;
+
+namespace dom {
+
+class SystemCallerGuarantee;
+template <typename T>
+class Optional;
+
+// This is the abstract class for any File backend. It must be nsISupports
+// because this class must be ref-counted and it has to work with IPC.
+class BlobImpl : public nsISupports {
+ public:
+  NS_DECLARE_STATIC_IID_ACCESSOR(BLOBIMPL_IID)
+  NS_DECL_THREADSAFE_ISUPPORTS
+
+  BlobImpl() = default;
+
+  virtual void GetName(nsAString& aName) const = 0;
+
+  virtual void GetDOMPath(nsAString& aName) const = 0;
+
+  virtual void SetDOMPath(const nsAString& aName) = 0;
+
+  virtual int64_t GetLastModified(ErrorResult& aRv) = 0;
+
+  virtual void GetMozFullPath(nsAString& aName,
+                              SystemCallerGuarantee /* unused */,
+                              ErrorResult& aRv) = 0;
+
+  virtual void GetMozFullPathInternal(nsAString& aFileName,
+                                      ErrorResult& aRv) = 0;
+
+  virtual uint64_t GetSize(ErrorResult& aRv) = 0;
+
+  virtual void GetType(nsAString& aType) = 0;
+
+  virtual void GetBlobImplType(nsAString& aBlobImplType) const = 0;
+
+  virtual size_t GetAllocationSize() const = 0;
+  virtual size_t GetAllocationSize(
+      FallibleTArray<BlobImpl*>& aVisitedBlobImpls) const = 0;
+
+  /**
+   * An effectively-unique serial number identifying this instance of FileImpl.
+   *
+   * Implementations should obtain a serial number from
+   * FileImplBase::NextSerialNumber().
+   */
+  virtual uint64_t GetSerialNumber() const = 0;
+
+  already_AddRefed<BlobImpl> Slice(const Optional<int64_t>& aStart,
+                                   const Optional<int64_t>& aEnd,
+                                   const nsAString& aContentType,
+                                   ErrorResult& aRv);
+
+  virtual already_AddRefed<BlobImpl> CreateSlice(uint64_t aStart,
+                                                 uint64_t aLength,
+                                                 const nsAString& aContentType,
+                                                 ErrorResult& aRv) const = 0;
+
+  virtual const nsTArray<RefPtr<BlobImpl>>* GetSubBlobImpls() const = 0;
+
+  virtual void CreateInputStream(nsIInputStream** aStream,
+                                 ErrorResult& aRv) const = 0;
+
+  virtual int64_t GetFileId() const = 0;
+
+  nsresult GetSendInfo(nsIInputStream** aBody, uint64_t* aContentLength,
+                       nsACString& aContentType, nsACString& aCharset);
+
+  virtual void SetLazyData(const nsAString& aName,
+                           const nsAString& aContentType, uint64_t aLength,
+                           int64_t aLastModifiedDate) = 0;
+
+  virtual bool IsMemoryFile() const = 0;
+
+  virtual bool IsFile() const = 0;
+
+  // Returns true if the BlobImpl is backed by an nsIFile and the underlying
+  // file is a directory.
+  virtual bool IsDirectory() const { return false; }
+
+ protected:
+  virtual ~BlobImpl() = default;
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(BlobImpl, BLOBIMPL_IID)
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // mozilla_dom_BlobImpl_h
diff --git a/dom/file/BlobSet.cpp b/dom/file/BlobSet.cpp
new file mode 100644
index 0000000000..6ae1774296
--- /dev/null
+++ b/dom/file/BlobSet.cpp
@@ -0,0 +1,83 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/BlobSet.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/dom/File.h"
+#include "MemoryBlobImpl.h"
+#include "MultipartBlobImpl.h"
+#include "StringBlobImpl.h"
+
+namespace mozilla::dom {
+
+nsresult BlobSet::AppendVoidPtr(const void* aData, uint32_t aLength) {
+  NS_ENSURE_ARG_POINTER(aData);
+  if (!aLength) {
+    return NS_OK;
+  }
+
+  void* data = malloc(aLength);
+  if (!data) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  memcpy((char*)data, aData, aLength);
+
+  RefPtr<BlobImpl> blobImpl = new MemoryBlobImpl(data, aLength, u""_ns);
+  return AppendBlobImpl(blobImpl);
+}
+
+nsresult BlobSet::AppendUTF8String(const nsACString& aUTF8String,
+                                   bool nativeEOL) {
+  nsCString utf8Str;
+  if (NS_WARN_IF(!utf8Str.Assign(aUTF8String, mozilla::fallible))) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  if (nativeEOL) {
+    if (utf8Str.Contains('\r')) {
+      if (NS_WARN_IF(
+              !utf8Str.ReplaceSubstring("\r\n", "\n", mozilla::fallible) ||
+              !utf8Str.ReplaceSubstring("\r", "\n", mozilla::fallible))) {
+        return NS_ERROR_OUT_OF_MEMORY;
+      }
+    }
+#ifdef XP_WIN
+    if (NS_WARN_IF(
+            !utf8Str.ReplaceSubstring("\n", "\r\n", mozilla::fallible))) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+#endif
+  }
+
+  RefPtr<StringBlobImpl> blobImpl = StringBlobImpl::Create(utf8Str, u""_ns);
+  return AppendBlobImpl(blobImpl);
+}
+
+nsresult BlobSet::AppendBlobImpl(BlobImpl* aBlobImpl) {
+  NS_ENSURE_ARG_POINTER(aBlobImpl);
+
+  // If aBlobImpl is a MultipartBlobImpl, let's append the sub-blobImpls
+  // instead.
+  const nsTArray<RefPtr<BlobImpl>>* subBlobs = aBlobImpl->GetSubBlobImpls();
+  if (subBlobs) {
+    for (BlobImpl* subBlob : *subBlobs) {
+      nsresult rv = AppendBlobImpl(subBlob);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+    }
+
+    return NS_OK;
+  }
+
+  if (NS_WARN_IF(!mBlobImpls.AppendElement(aBlobImpl, fallible))) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+  return NS_OK;
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/BlobSet.h b/dom/file/BlobSet.h
new file mode 100644
index 0000000000..43955c4c88
--- /dev/null
+++ b/dom/file/BlobSet.h
@@ -0,0 +1,36 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_BlobSet_h
+#define mozilla_dom_BlobSet_h
+
+#include "jsapi.h"
+#include "mozilla/RefPtr.h"
+#include "nsString.h"
+#include "nsTArray.h"
+
+namespace mozilla::dom {
+
+class BlobImpl;
+
+class BlobSet final {
+ public:
+  [[nodiscard]] nsresult AppendVoidPtr(const void* aData, uint32_t aLength);
+
+  [[nodiscard]] nsresult AppendUTF8String(const nsACString& aUTF8String,
+                                          bool nativeEOL);
+
+  [[nodiscard]] nsresult AppendBlobImpl(BlobImpl* aBlobImpl);
+
+  FallibleTArray<RefPtr<BlobImpl>>& GetBlobImpls() { return mBlobImpls; }
+
+ private:
+  FallibleTArray<RefPtr<BlobImpl>> mBlobImpls;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_BlobSet_h
diff --git a/dom/file/EmptyBlobImpl.cpp b/dom/file/EmptyBlobImpl.cpp
new file mode 100644
index 0000000000..5fa1055b4d
--- /dev/null
+++ b/dom/file/EmptyBlobImpl.cpp
@@ -0,0 +1,34 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "EmptyBlobImpl.h"
+#include "nsStringStream.h"
+
+namespace mozilla::dom {
+
+already_AddRefed<BlobImpl> EmptyBlobImpl::CreateSlice(
+    uint64_t aStart, uint64_t aLength, const nsAString& aContentType,
+    ErrorResult& aRv) const {
+  MOZ_ASSERT(!aStart && !aLength);
+  RefPtr<BlobImpl> impl = new EmptyBlobImpl(aContentType);
+  return impl.forget();
+}
+
+void EmptyBlobImpl::CreateInputStream(nsIInputStream** aStream,
+                                      ErrorResult& aRv) const {
+  if (NS_WARN_IF(!aStream)) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return;
+  }
+
+  nsresult rv = NS_NewCStringInputStream(aStream, ""_ns);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    aRv.Throw(rv);
+    return;
+  }
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/EmptyBlobImpl.h b/dom/file/EmptyBlobImpl.h
new file mode 100644
index 0000000000..37dd39da18
--- /dev/null
+++ b/dom/file/EmptyBlobImpl.h
@@ -0,0 +1,41 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_EmptyBlobImpl_h
+#define mozilla_dom_EmptyBlobImpl_h
+
+#include "BaseBlobImpl.h"
+
+namespace mozilla::dom {
+
+class EmptyBlobImpl final : public BaseBlobImpl {
+ public:
+  NS_INLINE_DECL_REFCOUNTING_INHERITED(EmptyBlobImpl, BaseBlobImpl)
+
+  // Blob constructor.
+  explicit EmptyBlobImpl(const nsAString& aContentType)
+      : BaseBlobImpl(aContentType, 0 /* aLength */) {}
+
+  void CreateInputStream(nsIInputStream** aStream,
+                         ErrorResult& aRv) const override;
+
+  already_AddRefed<BlobImpl> CreateSlice(uint64_t aStart, uint64_t aLength,
+                                         const nsAString& aContentType,
+                                         ErrorResult& aRv) const override;
+
+  bool IsMemoryFile() const override { return true; }
+
+  void GetBlobImplType(nsAString& aBlobImplType) const override {
+    aBlobImplType = u"EmptyBlobImpl"_ns;
+  }
+
+ private:
+  ~EmptyBlobImpl() override = default;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_EmptyBlobImpl_h
diff --git a/dom/file/File.cpp b/dom/file/File.cpp
new file mode 100644
index 0000000000..9995d35c52
--- /dev/null
+++ b/dom/file/File.cpp
@@ -0,0 +1,202 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "File.h"
+#include "FileBlobImpl.h"
+#include "MemoryBlobImpl.h"
+#include "MultipartBlobImpl.h"
+#include "mozilla/dom/BlobBinding.h"
+#include "mozilla/dom/FileBinding.h"
+#include "mozilla/dom/FileCreatorHelper.h"
+#include "mozilla/dom/FileSystemUtils.h"
+#include "mozilla/dom/Promise.h"
+#include "nsIFile.h"
+#include "nsContentUtils.h"
+#include "nsXULAppAPI.h"
+
+namespace mozilla::dom {
+
+File::File(nsIGlobalObject* aGlobal, BlobImpl* aImpl) : Blob(aGlobal, aImpl) {
+  MOZ_ASSERT(aImpl->IsFile());
+}
+
+File::~File() = default;
+
+/* static */
+File* File::Create(nsIGlobalObject* aGlobal, BlobImpl* aImpl) {
+  MOZ_ASSERT(aImpl);
+  MOZ_ASSERT(aImpl->IsFile());
+
+  MOZ_ASSERT(aGlobal);
+  if (NS_WARN_IF(!aGlobal)) {
+    return nullptr;
+  }
+
+  return new File(aGlobal, aImpl);
+}
+
+/* static */
+already_AddRefed<File> File::CreateMemoryFileWithCustomLastModified(
+    nsIGlobalObject* aGlobal, void* aMemoryBuffer, uint64_t aLength,
+    const nsAString& aName, const nsAString& aContentType,
+    int64_t aLastModifiedDate) {
+  RefPtr<MemoryBlobImpl> blobImpl =
+      MemoryBlobImpl::CreateWithCustomLastModified(
+          aMemoryBuffer, aLength, aName, aContentType, aLastModifiedDate);
+  MOZ_ASSERT(blobImpl);
+
+  RefPtr<File> file = File::Create(aGlobal, blobImpl);
+  return file.forget();
+}
+
+/* static */
+already_AddRefed<File> File::CreateMemoryFileWithLastModifiedNow(
+    nsIGlobalObject* aGlobal, void* aMemoryBuffer, uint64_t aLength,
+    const nsAString& aName, const nsAString& aContentType) {
+  MOZ_ASSERT(aGlobal);
+
+  RefPtr<MemoryBlobImpl> blobImpl = MemoryBlobImpl::CreateWithLastModifiedNow(
+      aMemoryBuffer, aLength, aName, aContentType, aGlobal->GetRTPCallerType());
+  MOZ_ASSERT(blobImpl);
+
+  RefPtr<File> file = File::Create(aGlobal, blobImpl);
+  return file.forget();
+}
+
+/* static */
+already_AddRefed<File> File::CreateFromFile(nsIGlobalObject* aGlobal,
+                                            nsIFile* aFile) {
+  MOZ_DIAGNOSTIC_ASSERT(XRE_IsParentProcess());
+
+  MOZ_ASSERT(aGlobal);
+  if (NS_WARN_IF(!aGlobal)) {
+    return nullptr;
+  }
+
+  RefPtr<File> file = new File(aGlobal, new FileBlobImpl(aFile));
+  return file.forget();
+}
+
+/* static */
+already_AddRefed<File> File::CreateFromFile(nsIGlobalObject* aGlobal,
+                                            nsIFile* aFile,
+                                            const nsAString& aName,
+                                            const nsAString& aContentType) {
+  MOZ_DIAGNOSTIC_ASSERT(XRE_IsParentProcess());
+
+  MOZ_ASSERT(aGlobal);
+  if (NS_WARN_IF(!aGlobal)) {
+    return nullptr;
+  }
+
+  RefPtr<File> file =
+      new File(aGlobal, new FileBlobImpl(aFile, aName, aContentType));
+  return file.forget();
+}
+
+JSObject* File::WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto) {
+  return File_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+void File::GetName(nsAString& aFileName) const { mImpl->GetName(aFileName); }
+
+void File::GetRelativePath(nsAString& aPath) const {
+  aPath.Truncate();
+
+  nsAutoString path;
+  mImpl->GetDOMPath(path);
+
+  // WebkitRelativePath doesn't start with '/'
+  if (!path.IsEmpty()) {
+    MOZ_ASSERT(path[0] == FILESYSTEM_DOM_PATH_SEPARATOR_CHAR);
+    aPath.Assign(Substring(path, 1));
+  }
+}
+
+int64_t File::GetLastModified(ErrorResult& aRv) {
+  return mImpl->GetLastModified(aRv);
+}
+
+void File::GetMozFullPath(nsAString& aFilename,
+                          SystemCallerGuarantee aGuarantee, ErrorResult& aRv) {
+  mImpl->GetMozFullPath(aFilename, aGuarantee, aRv);
+}
+
+void File::GetMozFullPathInternal(nsAString& aFileName, ErrorResult& aRv) {
+  mImpl->GetMozFullPathInternal(aFileName, aRv);
+}
+
+/* static */
+already_AddRefed<File> File::Constructor(const GlobalObject& aGlobal,
+                                         const Sequence<BlobPart>& aData,
+                                         const nsAString& aName,
+                                         const FilePropertyBag& aBag,
+                                         ErrorResult& aRv) {
+  RefPtr<MultipartBlobImpl> impl = new MultipartBlobImpl(aName);
+
+  nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(aGlobal.GetAsSupports());
+  MOZ_ASSERT(global);
+
+  nsAutoString type(aBag.mType);
+  MakeValidBlobType(type);
+  impl->InitializeBlob(aData, type, aBag.mEndings == EndingType::Native,
+                       global->GetRTPCallerType(), aRv);
+  if (aRv.Failed()) {
+    return nullptr;
+  }
+  MOZ_ASSERT(impl->IsFile());
+
+  if (aBag.mLastModified.WasPassed()) {
+    impl->SetLastModified(aBag.mLastModified.Value());
+  }
+
+  RefPtr<File> file = new File(global, impl);
+  return file.forget();
+}
+
+/* static */
+already_AddRefed<Promise> File::CreateFromNsIFile(
+    const GlobalObject& aGlobal, nsIFile* aData,
+    const ChromeFilePropertyBag& aBag, SystemCallerGuarantee aGuarantee,
+    ErrorResult& aRv) {
+  nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(aGlobal.GetAsSupports());
+
+  MOZ_ASSERT(global);
+  if (NS_WARN_IF(!global)) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return nullptr;
+  }
+
+  RefPtr<Promise> promise =
+      FileCreatorHelper::CreateFile(global, aData, aBag, true, aRv);
+  return promise.forget();
+}
+
+/* static */
+already_AddRefed<Promise> File::CreateFromFileName(
+    const GlobalObject& aGlobal, const nsAString& aPath,
+    const ChromeFilePropertyBag& aBag, SystemCallerGuarantee aGuarantee,
+    ErrorResult& aRv) {
+  nsCOMPtr<nsIFile> file;
+  aRv = NS_NewLocalFile(aPath, false, getter_AddRefs(file));
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(aGlobal.GetAsSupports());
+
+  MOZ_ASSERT(global);
+  if (NS_WARN_IF(!global)) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return nullptr;
+  }
+
+  RefPtr<Promise> promise =
+      FileCreatorHelper::CreateFile(global, file, aBag, false, aRv);
+  return promise.forget();
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/File.h b/dom/file/File.h
new file mode 100644
index 0000000000..279b91dd93
--- /dev/null
+++ b/dom/file/File.h
@@ -0,0 +1,103 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_File_h
+#define mozilla_dom_File_h
+
+#include "mozilla/dom/Blob.h"
+
+class nsIFile;
+
+namespace mozilla::dom {
+
+struct ChromeFilePropertyBag;
+struct FilePropertyBag;
+class Promise;
+
+class File final : public Blob {
+  friend class Blob;
+
+ public:
+  // Note: BlobImpl must be a File in order to use this method.
+  // Check impl->IsFile().
+  static File* Create(nsIGlobalObject* aGlobal, BlobImpl* aImpl);
+
+  // The returned File takes ownership of aMemoryBuffer. aMemoryBuffer will be
+  // freed by free so it must be allocated by malloc or something
+  // compatible with it.
+  static already_AddRefed<File> CreateMemoryFileWithLastModifiedNow(
+      nsIGlobalObject* aGlobal, void* aMemoryBuffer, uint64_t aLength,
+      const nsAString& aName, const nsAString& aContentType);
+
+  // You should not use this method! Please consider to use the
+  // CreateMemoryFileWithLastModifiedNow.
+  static already_AddRefed<File> CreateMemoryFileWithCustomLastModified(
+      nsIGlobalObject* aGlobal, void* aMemoryBuffer, uint64_t aLength,
+      const nsAString& aName, const nsAString& aContentType,
+      int64_t aLastModifiedDate);
+
+  // This method creates a BlobFileImpl for the new File object. This is
+  // thread-safe, cross-process, cross-thread as any other BlobImpl, but, when
+  // GetType() is called, it must dispatch a runnable to the main-thread in
+  // order to use nsIMIMEService.
+  // Would be nice if we try to avoid to use this method outside the
+  // main-thread to avoid extra runnables.
+  static already_AddRefed<File> CreateFromFile(nsIGlobalObject* aGlobal,
+                                               nsIFile* aFile);
+
+  static already_AddRefed<File> CreateFromFile(nsIGlobalObject* aGlobal,
+                                               nsIFile* aFile,
+                                               const nsAString& aName,
+                                               const nsAString& aContentType);
+
+  // WebIDL methods
+
+  JSObject* WrapObject(JSContext* cx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+  // File constructor
+  static already_AddRefed<File> Constructor(const GlobalObject& aGlobal,
+                                            const Sequence<BlobPart>& aData,
+                                            const nsAString& aName,
+                                            const FilePropertyBag& aBag,
+                                            ErrorResult& aRv);
+
+  // ChromeOnly
+  static already_AddRefed<Promise> CreateFromFileName(
+      const GlobalObject& aGlobal, const nsAString& aPath,
+      const ChromeFilePropertyBag& aBag, SystemCallerGuarantee aGuarantee,
+      ErrorResult& aRv);
+
+  // ChromeOnly
+  static already_AddRefed<Promise> CreateFromNsIFile(
+      const GlobalObject& aGlobal, nsIFile* aData,
+      const ChromeFilePropertyBag& aBag, SystemCallerGuarantee aGuarantee,
+      ErrorResult& aRv);
+
+  void GetName(nsAString& aFileName) const;
+
+  int64_t GetLastModified(ErrorResult& aRv);
+
+  void GetRelativePath(nsAString& aPath) const;
+
+  void GetMozFullPath(nsAString& aFilename, SystemCallerGuarantee aGuarantee,
+                      ErrorResult& aRv);
+
+  void GetMozFullPathInternal(nsAString& aFileName, ErrorResult& aRv);
+
+ protected:
+  bool HasFileInterface() const override { return true; }
+
+ private:
+  // File constructor should never be used directly. Use Blob::Create or
+  // File::Create.
+  File(nsIGlobalObject* aGlobal, BlobImpl* aImpl);
+  ~File() override;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_File_h
diff --git a/dom/file/FileBlobImpl.cpp b/dom/file/FileBlobImpl.cpp
new file mode 100644
index 0000000000..af80476e1a
--- /dev/null
+++ b/dom/file/FileBlobImpl.cpp
@@ -0,0 +1,294 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "FileBlobImpl.h"
+#include "BaseBlobImpl.h"
+#include "mozilla/SlicedInputStream.h"
+#include "mozilla/dom/WorkerPrivate.h"
+#include "mozilla/dom/WorkerRunnable.h"
+#include "nsCExternalHandlerService.h"
+#include "nsIFile.h"
+#include "nsIFileStreams.h"
+#include "nsIMIMEService.h"
+#include "nsNetUtil.h"
+#include "nsStreamUtils.h"
+
+namespace mozilla::dom {
+
+FileBlobImpl::FileBlobImpl(nsIFile* aFile)
+    : mMutex("FileBlobImpl::mMutex"),
+      mFile(aFile),
+      mSerialNumber(BaseBlobImpl::NextSerialNumber()),
+      mStart(0),
+      mFileId(-1),
+      mIsFile(true),
+      mWholeFile(true) {
+  MOZ_ASSERT(mFile, "must have file");
+  MOZ_ASSERT(XRE_IsParentProcess());
+  // Lazily get the content type and size
+  mContentType.SetIsVoid(true);
+  mMozFullPath.SetIsVoid(true);
+  mFile->GetLeafName(mName);
+}
+
+FileBlobImpl::FileBlobImpl(const nsAString& aName,
+                           const nsAString& aContentType, uint64_t aLength,
+                           nsIFile* aFile)
+    : mMutex("FileBlobImpl::mMutex"),
+      mFile(aFile),
+      mContentType(aContentType),
+      mName(aName),
+      mSerialNumber(BaseBlobImpl::NextSerialNumber()),
+      mStart(0),
+      mFileId(-1),
+      mLength(Some(aLength)),
+      mIsFile(true),
+      mWholeFile(true) {
+  MOZ_ASSERT(mFile, "must have file");
+  MOZ_ASSERT(XRE_IsParentProcess());
+  mMozFullPath.SetIsVoid(true);
+}
+
+FileBlobImpl::FileBlobImpl(const nsAString& aName,
+                           const nsAString& aContentType, uint64_t aLength,
+                           nsIFile* aFile, int64_t aLastModificationDate)
+    : mMutex("FileBlobImpl::mMutex"),
+      mFile(aFile),
+      mContentType(aContentType),
+      mName(aName),
+      mSerialNumber(BaseBlobImpl::NextSerialNumber()),
+      mStart(0),
+      mFileId(-1),
+      mLength(Some(aLength)),
+      mLastModified(Some(aLastModificationDate)),
+      mIsFile(true),
+      mWholeFile(true) {
+  MOZ_ASSERT(mFile, "must have file");
+  MOZ_ASSERT(XRE_IsParentProcess());
+  mMozFullPath.SetIsVoid(true);
+}
+
+FileBlobImpl::FileBlobImpl(nsIFile* aFile, const nsAString& aName,
+                           const nsAString& aContentType)
+    : mMutex("FileBlobImpl::mMutex"),
+      mFile(aFile),
+      mContentType(aContentType),
+      mName(aName),
+      mSerialNumber(BaseBlobImpl::NextSerialNumber()),
+      mStart(0),
+      mFileId(-1),
+      mIsFile(true),
+      mWholeFile(true) {
+  MOZ_ASSERT(mFile, "must have file");
+  MOZ_ASSERT(XRE_IsParentProcess());
+  if (aContentType.IsEmpty()) {
+    // Lazily get the content type and size
+    mContentType.SetIsVoid(true);
+  }
+
+  mMozFullPath.SetIsVoid(true);
+}
+
+FileBlobImpl::FileBlobImpl(const FileBlobImpl* aOther, uint64_t aStart,
+                           uint64_t aLength, const nsAString& aContentType)
+    : mMutex("FileBlobImpl::mMutex"),
+      mFile(aOther->mFile),
+      mContentType(aContentType),
+      mSerialNumber(BaseBlobImpl::NextSerialNumber()),
+      mStart(aOther->mStart + aStart),
+      mFileId(-1),
+      mLength(Some(aLength)),
+      mIsFile(false),
+      mWholeFile(false) {
+  MOZ_ASSERT(mFile, "must have file");
+  MOZ_ASSERT(XRE_IsParentProcess());
+  mMozFullPath = aOther->mMozFullPath;
+}
+
+already_AddRefed<BlobImpl> FileBlobImpl::CreateSlice(
+    uint64_t aStart, uint64_t aLength, const nsAString& aContentType,
+    ErrorResult& aRv) const {
+  RefPtr<FileBlobImpl> impl =
+      new FileBlobImpl(this, aStart, aLength, aContentType);
+  return impl.forget();
+}
+
+void FileBlobImpl::GetMozFullPathInternal(nsAString& aFilename,
+                                          ErrorResult& aRv) {
+  MOZ_ASSERT(mIsFile, "Should only be called on files");
+
+  MutexAutoLock lock(mMutex);
+
+  if (!mMozFullPath.IsVoid()) {
+    aFilename = mMozFullPath;
+    return;
+  }
+
+  aRv = mFile->GetPath(aFilename);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  mMozFullPath = aFilename;
+}
+
+uint64_t FileBlobImpl::GetSize(ErrorResult& aRv) {
+  MutexAutoLock lock(mMutex);
+
+  if (mLength.isNothing()) {
+    MOZ_ASSERT(mWholeFile,
+               "Should only use lazy size when using the whole file");
+    int64_t fileSize;
+    aRv = mFile->GetFileSize(&fileSize);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return 0;
+    }
+
+    if (fileSize < 0) {
+      aRv.Throw(NS_ERROR_FAILURE);
+      return 0;
+    }
+
+    mLength.emplace(fileSize);
+  }
+
+  return mLength.value();
+}
+
+class FileBlobImpl::GetTypeRunnable final : public WorkerMainThreadRunnable {
+ public:
+  GetTypeRunnable(WorkerPrivate* aWorkerPrivate, FileBlobImpl* aBlobImpl,
+                  const MutexAutoLock& aProofOfLock)
+      : WorkerMainThreadRunnable(aWorkerPrivate, "FileBlobImpl :: GetType"_ns),
+        mBlobImpl(aBlobImpl),
+        mProofOfLock(aProofOfLock) {
+    MOZ_ASSERT(aBlobImpl);
+    aWorkerPrivate->AssertIsOnWorkerThread();
+  }
+
+  bool MainThreadRun() override {
+    MOZ_ASSERT(NS_IsMainThread());
+
+    nsAutoString type;
+    mBlobImpl->GetTypeInternal(type, mProofOfLock);
+    return true;
+  }
+
+ private:
+  ~GetTypeRunnable() override = default;
+
+  RefPtr<FileBlobImpl> mBlobImpl;
+  const MutexAutoLock& mProofOfLock;
+};
+
+void FileBlobImpl::GetType(nsAString& aType) {
+  MutexAutoLock lock(mMutex);
+  GetTypeInternal(aType, lock);
+}
+
+void FileBlobImpl::GetTypeInternal(nsAString& aType,
+                                   const MutexAutoLock& aProofOfLock) {
+  aType.Truncate();
+
+  if (mContentType.IsVoid()) {
+    MOZ_ASSERT(mWholeFile,
+               "Should only use lazy ContentType when using the whole file");
+
+    if (!NS_IsMainThread()) {
+      WorkerPrivate* workerPrivate = GetCurrentThreadWorkerPrivate();
+      if (!workerPrivate) {
+        // I have no idea in which thread this method is called. We cannot
+        // return any valid value.
+        return;
+      }
+
+      RefPtr<GetTypeRunnable> runnable =
+          new GetTypeRunnable(workerPrivate, this, aProofOfLock);
+
+      ErrorResult rv;
+      runnable->Dispatch(Canceling, rv);
+      if (NS_WARN_IF(rv.Failed())) {
+        rv.SuppressException();
+        return;
+      }
+    } else {
+      nsresult rv;
+      nsCOMPtr<nsIMIMEService> mimeService =
+          do_GetService(NS_MIMESERVICE_CONTRACTID, &rv);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return;
+      }
+
+      nsAutoCString mimeType;
+      rv = mimeService->GetTypeFromFile(mFile, mimeType);
+      if (NS_FAILED(rv)) {
+        mimeType.Truncate();
+      }
+
+      AppendUTF8toUTF16(mimeType, mContentType);
+      mContentType.SetIsVoid(false);
+    }
+  }
+
+  aType = mContentType;
+}
+
+void FileBlobImpl::GetBlobImplType(nsAString& aBlobImplType) const {
+  aBlobImplType = u"FileBlobImpl"_ns;
+}
+
+int64_t FileBlobImpl::GetLastModified(ErrorResult& aRv) {
+  MOZ_ASSERT(mIsFile, "Should only be called on files");
+
+  MutexAutoLock lock(mMutex);
+
+  if (mLastModified.isNothing()) {
+    PRTime msecs;
+    aRv = mFile->GetLastModifiedTime(&msecs);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return 0;
+    }
+
+    mLastModified.emplace(int64_t(msecs));
+  }
+
+  return mLastModified.value();
+}
+
+const uint32_t sFileStreamFlags =
+    nsIFileInputStream::CLOSE_ON_EOF | nsIFileInputStream::REOPEN_ON_REWIND |
+    nsIFileInputStream::DEFER_OPEN | nsIFileInputStream::SHARE_DELETE;
+
+void FileBlobImpl::CreateInputStream(nsIInputStream** aStream,
+                                     ErrorResult& aRv) const {
+  nsCOMPtr<nsIInputStream> stream;
+  aRv = NS_NewLocalFileInputStream(getter_AddRefs(stream), mFile, -1, -1,
+                                   sFileStreamFlags);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  if (mWholeFile) {
+    stream.forget(aStream);
+    return;
+  }
+
+  MOZ_ASSERT(mLength.isSome());
+
+  RefPtr<SlicedInputStream> slicedInputStream =
+      new SlicedInputStream(stream.forget(), mStart, mLength.value());
+  slicedInputStream.forget(aStream);
+}
+
+bool FileBlobImpl::IsDirectory() const {
+  bool isDirectory = false;
+  if (mFile) {
+    mFile->IsDirectory(&isDirectory);
+  }
+  return isDirectory;
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/FileBlobImpl.h b/dom/file/FileBlobImpl.h
new file mode 100644
index 0000000000..84565dbd4b
--- /dev/null
+++ b/dom/file/FileBlobImpl.h
@@ -0,0 +1,157 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_FileBlobImpl_h
+#define mozilla_dom_FileBlobImpl_h
+
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/BlobImpl.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Mutex.h"
+#include "nsCOMPtr.h"
+
+class nsIFile;
+
+namespace mozilla::dom {
+
+class FileBlobImpl : public BlobImpl {
+ public:
+  NS_INLINE_DECL_REFCOUNTING_INHERITED(FileBlobImpl, BlobImpl)
+
+  // Create as a file
+  explicit FileBlobImpl(nsIFile* aFile);
+
+  // Create as a file
+  FileBlobImpl(const nsAString& aName, const nsAString& aContentType,
+               uint64_t aLength, nsIFile* aFile);
+
+  FileBlobImpl(const nsAString& aName, const nsAString& aContentType,
+               uint64_t aLength, nsIFile* aFile, int64_t aLastModificationDate);
+
+  // Create as a file with custom name
+  FileBlobImpl(nsIFile* aFile, const nsAString& aName,
+               const nsAString& aContentType);
+
+  void GetName(nsAString& aName) const override {
+    MOZ_ASSERT(mIsFile, "Should only be called on files");
+    aName = mName;
+  }
+
+  void SetName(const nsAString& aName) { mName = aName; }
+
+  void GetDOMPath(nsAString& aPath) const override {
+    MOZ_ASSERT(mIsFile, "Should only be called on files");
+    aPath = mPath;
+  }
+
+  void SetDOMPath(const nsAString& aPath) override {
+    MOZ_ASSERT(mIsFile, "Should only be called on files");
+    mPath = aPath;
+  }
+
+  int64_t GetLastModified(ErrorResult& aRv) override;
+
+  void GetMozFullPath(nsAString& aFileName, SystemCallerGuarantee /* unused */,
+                      ErrorResult& aRv) override {
+    MOZ_ASSERT(mIsFile, "Should only be called on files");
+
+    GetMozFullPathInternal(aFileName, aRv);
+  }
+
+  void GetMozFullPathInternal(nsAString& aFilename, ErrorResult& aRv) override;
+
+  uint64_t GetSize(ErrorResult& aRv) override;
+
+  void GetType(nsAString& aType) override;
+
+  void GetBlobImplType(nsAString& aBlobImplType) const override;
+
+  size_t GetAllocationSize() const override { return 0; }
+
+  size_t GetAllocationSize(
+      FallibleTArray<BlobImpl*>& aVisitedBlobImpls) const override {
+    return GetAllocationSize();
+  }
+
+  uint64_t GetSerialNumber() const override { return mSerialNumber; }
+
+  const nsTArray<RefPtr<BlobImpl>>* GetSubBlobImpls() const override {
+    return nullptr;
+  }
+
+  void CreateInputStream(nsIInputStream** aStream,
+                         ErrorResult& aRv) const override;
+
+  int64_t GetFileId() const override { return mFileId; }
+
+  void SetLazyData(const nsAString& aName, const nsAString& aContentType,
+                   uint64_t aLength, int64_t aLastModifiedDate) override {
+    mName = aName;
+    mContentType = aContentType;
+    mIsFile = !aName.IsVoid();
+    mLength.emplace(aLength);
+    mLastModified.emplace(aLastModifiedDate);
+  }
+
+  bool IsMemoryFile() const override { return false; }
+
+  bool IsFile() const override { return mIsFile; }
+
+  bool IsDirectory() const override;
+
+  void SetType(const nsAString& aType) { mContentType = aType; }
+
+  void SetFileId(int64_t aFileId) { mFileId = aFileId; }
+
+  void SetEmptySize() { mLength.emplace(0); }
+
+  void SetMozFullPath(const nsAString& aPath) { mMozFullPath = aPath; }
+
+  void SetLastModified(int64_t aLastModified) {
+    mLastModified.emplace(aLastModified);
+  }
+
+ protected:
+  ~FileBlobImpl() override = default;
+
+  // Create slice
+  FileBlobImpl(const FileBlobImpl* aOther, uint64_t aStart, uint64_t aLength,
+               const nsAString& aContentType);
+
+  already_AddRefed<BlobImpl> CreateSlice(uint64_t aStart, uint64_t aLength,
+                                         const nsAString& aContentType,
+                                         ErrorResult& aRv) const override;
+
+  class GetTypeRunnable;
+  void GetTypeInternal(nsAString& aType, const MutexAutoLock& aProofOfLock);
+
+  // FileBlobImpl has getter methods with lazy initialization. Because any
+  // BlobImpl must work thread-safe, we use a mutex.
+  Mutex mMutex MOZ_UNANNOTATED;
+
+  nsCOMPtr<nsIFile> mFile;
+
+  nsString mContentType;
+  nsString mName;
+  nsString mPath;  // The path relative to a directory chosen by the user
+  nsString mMozFullPath;
+
+  const uint64_t mSerialNumber;
+  uint64_t mStart;
+
+  int64_t mFileId;
+
+  Maybe<uint64_t> mLength;
+
+  Maybe<int64_t> mLastModified;
+
+  bool mIsFile;
+  bool mWholeFile;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_FileBlobImpl_h
diff --git a/dom/file/FileCreatorHelper.cpp b/dom/file/FileCreatorHelper.cpp
new file mode 100644
index 0000000000..2c4ee4c041
--- /dev/null
+++ b/dom/file/FileCreatorHelper.cpp
@@ -0,0 +1,67 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "FileCreatorHelper.h"
+
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/FileBinding.h"
+#include "mozilla/dom/FileCreatorChild.h"
+#include "mozilla/ipc/BackgroundChild.h"
+#include "mozilla/ipc/PBackgroundChild.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/dom/Promise.h"
+#include "nsContentUtils.h"
+#include "nsPIDOMWindow.h"
+#include "nsProxyRelease.h"
+#include "nsIFile.h"
+
+// Undefine the macro of CreateFile to avoid FileCreatorHelper#CreateFile being
+// replaced by FileCreatorHelper#CreateFileW.
+#ifdef CreateFile
+#  undef CreateFile
+#endif
+
+namespace mozilla::dom {
+
+/* static */
+already_AddRefed<Promise> FileCreatorHelper::CreateFile(
+    nsIGlobalObject* aGlobalObject, nsIFile* aFile,
+    const ChromeFilePropertyBag& aBag, bool aIsFromNsIFile, ErrorResult& aRv) {
+  MOZ_DIAGNOSTIC_ASSERT(NS_IsMainThread());
+
+  RefPtr<Promise> promise = Promise::Create(aGlobalObject, aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  nsAutoString path;
+  aRv = aFile->GetPath(path);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  // Register this component to PBackground.
+  mozilla::ipc::PBackgroundChild* actorChild =
+      mozilla::ipc::BackgroundChild::GetOrCreateForCurrentThread();
+  if (NS_WARN_IF(!actorChild)) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return nullptr;
+  }
+
+  Maybe<int64_t> lastModified;
+  if (aBag.mLastModified.WasPassed()) {
+    lastModified.emplace(aBag.mLastModified.Value());
+  }
+
+  PFileCreatorChild* actor = actorChild->SendPFileCreatorConstructor(
+      path, aBag.mType, aBag.mName, lastModified, aBag.mExistenceCheck,
+      aIsFromNsIFile);
+
+  static_cast<FileCreatorChild*>(actor)->SetPromise(promise);
+  return promise.forget();
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/FileCreatorHelper.h b/dom/file/FileCreatorHelper.h
new file mode 100644
index 0000000000..f0b666cc58
--- /dev/null
+++ b/dom/file/FileCreatorHelper.h
@@ -0,0 +1,43 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_FileCreatorHelper_h
+#define mozilla_dom_FileCreatorHelper_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/RefPtr.h"
+#include "nsISupportsImpl.h"
+
+// Undefine the macro of CreateFile to avoid FileCreatorHelper#CreateFile being
+// replaced by FileCreatorHelper#CreateFileW.
+#ifdef CreateFile
+#  undef CreateFile
+#endif
+
+class nsIFile;
+class nsIGlobalObject;
+
+namespace mozilla {
+class ErrorResult;
+
+namespace dom {
+
+struct ChromeFilePropertyBag;
+class Promise;
+
+class FileCreatorHelper final {
+ public:
+  static already_AddRefed<Promise> CreateFile(nsIGlobalObject* aGlobalObject,
+                                              nsIFile* aFile,
+                                              const ChromeFilePropertyBag& aBag,
+                                              bool aIsFromNsIFile,
+                                              ErrorResult& aRv);
+};
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // mozilla_dom_FileCreatorHelper_h
diff --git a/dom/file/FileList.cpp b/dom/file/FileList.cpp
new file mode 100644
index 0000000000..2cc7b0c7f1
--- /dev/null
+++ b/dom/file/FileList.cpp
@@ -0,0 +1,94 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/FileList.h"
+
+#include <new>
+#include <utility>
+#include "ErrorList.h"
+#include "js/RootingAPI.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/ErrorResult.h"
+#include "mozilla/MacroForEach.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/dom/FileListBinding.h"
+#include "mozilla/fallible.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsCycleCollectionTraversalCallback.h"
+#include "nsISupports.h"
+#include "nsTArray.h"
+#include "nsWrapperCache.h"
+
+namespace mozilla::dom {
+
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(FileList, mFiles, mParent)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(FileList)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(FileList)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(FileList)
+
+FileList::FileList(nsISupports* aParent) : mParent(aParent) {}
+
+FileList::~FileList() = default;
+
+JSObject* FileList::WrapObject(JSContext* aCx,
+                               JS::Handle<JSObject*> aGivenProto) {
+  return mozilla::dom::FileList_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+bool FileList::Append(File* aFile) {
+  MOZ_ASSERT(aFile);
+  return mFiles.AppendElement(aFile, fallible);
+}
+
+bool FileList::Remove(uint32_t aIndex) {
+  if (aIndex < mFiles.Length()) {
+    mFiles.RemoveElementAt(aIndex);
+    return true;
+  }
+
+  return false;
+}
+
+void FileList::Clear() { return mFiles.Clear(); }
+
+File* FileList::Item(uint32_t aIndex) const {
+  if (aIndex >= mFiles.Length()) {
+    return nullptr;
+  }
+
+  return mFiles[aIndex];
+}
+
+File* FileList::IndexedGetter(uint32_t aIndex, bool& aFound) const {
+  aFound = aIndex < mFiles.Length();
+  return Item(aIndex);
+}
+
+void FileList::ToSequence(Sequence<RefPtr<File>>& aSequence,
+                          ErrorResult& aRv) const {
+  MOZ_ASSERT(aSequence.IsEmpty());
+  if (mFiles.IsEmpty()) {
+    return;
+  }
+
+  if (!aSequence.SetLength(mFiles.Length(), mozilla::fallible_t())) {
+    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+    return;
+  }
+
+  for (uint32_t i = 0; i < mFiles.Length(); ++i) {
+    aSequence[i] = mFiles[i];
+  }
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/FileList.h b/dom/file/FileList.h
new file mode 100644
index 0000000000..f36b25ba07
--- /dev/null
+++ b/dom/file/FileList.h
@@ -0,0 +1,68 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_FileList_h
+#define mozilla_dom_FileList_h
+
+#include <cstdint>
+#include "js/TypeDecls.h"
+#include "mozilla/Assertions.h"
+#include "nsCOMPtr.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsISupports.h"
+#include "nsTArray.h"
+#include "nsWrapperCache.h"
+
+class nsCycleCollectionTraversalCallback;
+template <class T>
+class RefPtr;
+
+namespace mozilla {
+class ErrorResult;
+namespace dom {
+
+class BlobImpls;
+class File;
+template <typename T>
+class Sequence;
+
+class FileList final : public nsISupports, public nsWrapperCache {
+ public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(FileList)
+
+  explicit FileList(nsISupports* aParent);
+
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+  nsISupports* GetParentObject() { return mParent; }
+
+  bool Append(File* aFile);
+
+  bool Remove(uint32_t aIndex);
+
+  void Clear();
+
+  File* Item(uint32_t aIndex) const;
+
+  File* IndexedGetter(uint32_t aIndex, bool& aFound) const;
+
+  uint32_t Length() const { return mFiles.Length(); }
+
+  void ToSequence(Sequence<RefPtr<File>>& aSequence, ErrorResult& aRv) const;
+
+ private:
+  ~FileList();
+
+  FallibleTArray<RefPtr<File>> mFiles;
+  nsCOMPtr<nsISupports> mParent;
+};
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // mozilla_dom_FileList_h
diff --git a/dom/file/FileReader.cpp b/dom/file/FileReader.cpp
new file mode 100644
index 0000000000..ca1d55c0d8
--- /dev/null
+++ b/dom/file/FileReader.cpp
@@ -0,0 +1,803 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "FileReader.h"
+
+#include "nsIGlobalObject.h"
+#include "nsITimer.h"
+
+#include "js/ArrayBuffer.h"  // JS::NewArrayBufferWithContents
+#include "mozilla/Base64.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/dom/DOMException.h"
+#include "mozilla/dom/DOMExceptionBinding.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/dom/FileReaderBinding.h"
+#include "mozilla/dom/ProgressEvent.h"
+#include "mozilla/dom/UnionTypes.h"
+#include "mozilla/dom/ScriptSettings.h"
+#include "mozilla/dom/WorkerCommon.h"
+#include "mozilla/dom/WorkerRef.h"
+#include "mozilla/dom/WorkerScope.h"
+#include "mozilla/Encoding.h"
+#include "mozilla/HoldDropJSObjects.h"
+#include "nsAlgorithm.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsDOMJSUtils.h"
+#include "nsError.h"
+#include "nsNetUtil.h"
+#include "nsStreamUtils.h"
+#include "nsThreadUtils.h"
+#include "xpcpublic.h"
+#include "nsReadableUtils.h"
+
+namespace mozilla::dom {
+
+#define ABORT_STR u"abort"
+#define LOAD_STR u"load"
+#define LOADSTART_STR u"loadstart"
+#define LOADEND_STR u"loadend"
+#define ERROR_STR u"error"
+#define PROGRESS_STR u"progress"
+
+const uint64_t kUnknownSize = uint64_t(-1);
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(FileReader)
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(FileReader,
+                                                  DOMEventTargetHelper)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mBlob)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mProgressNotifier)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mError)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(FileReader,
+                                                DOMEventTargetHelper)
+  tmp->Shutdown();
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mBlob)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mProgressNotifier)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mError)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_WEAK_REFERENCE
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN_INHERITED(FileReader, DOMEventTargetHelper)
+  NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mResultArrayBuffer)
+NS_IMPL_CYCLE_COLLECTION_TRACE_END
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(FileReader)
+  NS_INTERFACE_MAP_ENTRY_CONCRETE(FileReader)
+  NS_INTERFACE_MAP_ENTRY(nsITimerCallback)
+  NS_INTERFACE_MAP_ENTRY(nsIInputStreamCallback)
+  NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
+  NS_INTERFACE_MAP_ENTRY(nsINamed)
+NS_INTERFACE_MAP_END_INHERITING(DOMEventTargetHelper)
+
+NS_IMPL_ADDREF_INHERITED(FileReader, DOMEventTargetHelper)
+NS_IMPL_RELEASE_INHERITED(FileReader, DOMEventTargetHelper)
+
+class MOZ_RAII FileReaderDecreaseBusyCounter {
+  RefPtr<FileReader> mFileReader;
+
+ public:
+  explicit FileReaderDecreaseBusyCounter(FileReader* aFileReader)
+      : mFileReader(aFileReader) {}
+
+  ~FileReaderDecreaseBusyCounter() { mFileReader->DecreaseBusyCounter(); }
+};
+
+class FileReader::AsyncWaitRunnable final : public CancelableRunnable {
+ public:
+  explicit AsyncWaitRunnable(FileReader* aReader)
+      : CancelableRunnable("FileReader::AsyncWaitRunnable"), mReader(aReader) {}
+
+  NS_IMETHOD
+  Run() override {
+    if (mReader) {
+      mReader->InitialAsyncWait();
+    }
+    return NS_OK;
+  }
+
+  nsresult Cancel() override {
+    mReader = nullptr;
+    return NS_OK;
+  }
+
+ public:
+  RefPtr<FileReader> mReader;
+};
+
+void FileReader::RootResultArrayBuffer() { mozilla::HoldJSObjects(this); }
+
+// FileReader constructors/initializers
+
+FileReader::FileReader(nsIGlobalObject* aGlobal, WeakWorkerRef* aWorkerRef)
+    : DOMEventTargetHelper(aGlobal),
+      mFileData(nullptr),
+      mDataLen(0),
+      mDataFormat(FILE_AS_BINARY),
+      mResultArrayBuffer(nullptr),
+      mProgressEventWasDelayed(false),
+      mTimerIsActive(false),
+      mReadyState(EMPTY),
+      mTotal(0),
+      mTransferred(0),
+      mBusyCount(0),
+      mWeakWorkerRef(aWorkerRef) {
+  MOZ_ASSERT(aGlobal);
+  MOZ_ASSERT_IF(NS_IsMainThread(), !mWeakWorkerRef);
+
+  if (NS_IsMainThread()) {
+    mTarget = aGlobal->EventTargetFor(TaskCategory::Other);
+  } else {
+    mTarget = GetCurrentSerialEventTarget();
+  }
+
+  SetDOMStringToNull(mResult);
+}
+
+FileReader::~FileReader() {
+  Shutdown();
+  DropJSObjects(this);
+}
+
+/* static */
+already_AddRefed<FileReader> FileReader::Constructor(
+    const GlobalObject& aGlobal) {
+  nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(aGlobal.GetAsSupports());
+  RefPtr<WeakWorkerRef> workerRef;
+
+  if (!NS_IsMainThread()) {
+    JSContext* cx = aGlobal.Context();
+    WorkerPrivate* workerPrivate = GetWorkerPrivateFromContext(cx);
+
+    workerRef = WeakWorkerRef::Create(workerPrivate);
+  }
+
+  RefPtr<FileReader> fileReader = new FileReader(global, workerRef);
+
+  return fileReader.forget();
+}
+
+// nsIInterfaceRequestor
+
+NS_IMETHODIMP
+FileReader::GetInterface(const nsIID& aIID, void** aResult) {
+  return QueryInterface(aIID, aResult);
+}
+
+void FileReader::GetResult(JSContext* aCx,
+                           Nullable<OwningStringOrArrayBuffer>& aResult) {
+  JS::Rooted<JS::Value> result(aCx);
+
+  if (mDataFormat == FILE_AS_ARRAYBUFFER) {
+    if (mReadyState != DONE || !mResultArrayBuffer ||
+        !aResult.SetValue().SetAsArrayBuffer().Init(mResultArrayBuffer)) {
+      aResult.SetNull();
+    }
+
+    return;
+  }
+
+  if (mReadyState != DONE || mResult.IsVoid()) {
+    aResult.SetNull();
+    return;
+  }
+
+  aResult.SetValue().SetAsString() = mResult;
+}
+
+void FileReader::OnLoadEndArrayBuffer() {
+  AutoJSAPI jsapi;
+  if (!jsapi.Init(GetParentObject())) {
+    FreeDataAndDispatchError(NS_ERROR_FAILURE);
+    return;
+  }
+
+  RootResultArrayBuffer();
+
+  JSContext* cx = jsapi.cx();
+
+  mResultArrayBuffer = JS::NewArrayBufferWithContents(cx, mDataLen, mFileData);
+  if (mResultArrayBuffer) {
+    mFileData = nullptr;  // Transfer ownership
+    FreeDataAndDispatchSuccess();
+    return;
+  }
+
+  // Let's handle the error status.
+
+  JS::Rooted<JS::Value> exceptionValue(cx);
+  if (!JS_GetPendingException(cx, &exceptionValue) ||
+      // This should not really happen, exception should always be an object.
+      !exceptionValue.isObject()) {
+    JS_ClearPendingException(jsapi.cx());
+    FreeDataAndDispatchError(NS_ERROR_OUT_OF_MEMORY);
+    return;
+  }
+
+  JS_ClearPendingException(jsapi.cx());
+
+  JS::Rooted<JSObject*> exceptionObject(cx, &exceptionValue.toObject());
+  JSErrorReport* er = JS_ErrorFromException(cx, exceptionObject);
+  if (!er || er->message()) {
+    FreeDataAndDispatchError(NS_ERROR_OUT_OF_MEMORY);
+    return;
+  }
+
+  nsAutoString errorName;
+  JSLinearString* name = js::GetErrorTypeName(cx, er->exnType);
+  if (name) {
+    AssignJSLinearString(errorName, name);
+  }
+
+  nsAutoCString errorMsg(er->message().c_str());
+  nsAutoCString errorNameC = NS_LossyConvertUTF16toASCII(errorName);
+  // XXX Code selected arbitrarily
+  mError =
+      new DOMException(NS_ERROR_DOM_INVALID_STATE_ERR, errorMsg, errorNameC,
+                       DOMException_Binding::INVALID_STATE_ERR);
+
+  FreeDataAndDispatchError();
+}
+
+nsresult FileReader::DoAsyncWait() {
+  nsresult rv = IncreaseBusyCounter();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  rv = mAsyncStream->AsyncWait(this,
+                               /* aFlags*/ 0,
+                               /* aRequestedCount */ 0, mTarget);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    DecreaseBusyCounter();
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+namespace {
+
+void PopulateBufferForBinaryString(char16_t* aDest, const char* aSource,
+                                   uint32_t aCount) {
+  // Zero-extend each char to char16_t.
+  ConvertLatin1toUtf16(Span(aSource, aCount), Span(aDest, aCount));
+}
+
+nsresult ReadFuncBinaryString(nsIInputStream* aInputStream, void* aClosure,
+                              const char* aFromRawSegment, uint32_t aToOffset,
+                              uint32_t aCount, uint32_t* aWriteCount) {
+  char16_t* dest = static_cast<char16_t*>(aClosure) + aToOffset;
+  PopulateBufferForBinaryString(dest, aFromRawSegment, aCount);
+  *aWriteCount = aCount;
+  return NS_OK;
+}
+
+}  // namespace
+
+nsresult FileReader::DoReadData(uint64_t aCount) {
+  MOZ_ASSERT(mAsyncStream);
+
+  uint32_t bytesRead = 0;
+
+  if (mDataFormat == FILE_AS_BINARY) {
+    // Continuously update our binary string as data comes in
+    CheckedInt<uint64_t> size{mResult.Length()};
+    size += aCount;
+
+    if (!size.isValid() || size.value() > UINT32_MAX || size.value() > mTotal) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+
+    uint32_t lenBeforeRead = mResult.Length();
+    MOZ_ASSERT(lenBeforeRead == mDataLen, "unexpected mResult length");
+
+    mResult.SetLength(lenBeforeRead + aCount);
+    char16_t* currentPos = mResult.BeginWriting() + lenBeforeRead;
+
+    if (NS_InputStreamIsBuffered(mAsyncStream)) {
+      nsresult rv = mAsyncStream->ReadSegments(ReadFuncBinaryString, currentPos,
+                                               aCount, &bytesRead);
+      NS_ENSURE_SUCCESS(rv, NS_OK);
+    } else {
+      while (aCount > 0) {
+        char tmpBuffer[4096];
+        uint32_t minCount =
+            XPCOM_MIN(aCount, static_cast<uint64_t>(sizeof(tmpBuffer)));
+        uint32_t read;
+
+        nsresult rv = mAsyncStream->Read(tmpBuffer, minCount, &read);
+        if (rv == NS_BASE_STREAM_CLOSED) {
+          rv = NS_OK;
+        }
+
+        NS_ENSURE_SUCCESS(rv, NS_OK);
+
+        if (read == 0) {
+          // The stream finished too early.
+          return NS_ERROR_OUT_OF_MEMORY;
+        }
+
+        PopulateBufferForBinaryString(currentPos, tmpBuffer, read);
+
+        currentPos += read;
+        aCount -= read;
+        bytesRead += read;
+      }
+    }
+
+    MOZ_ASSERT(size.value() == lenBeforeRead + bytesRead);
+    mResult.Truncate(size.value());
+  } else {
+    CheckedInt<uint64_t> size = mDataLen;
+    size += aCount;
+
+    // Update memory buffer to reflect the contents of the file
+    if (!size.isValid() ||
+        // PR_Realloc doesn't support over 4GB memory size even if 64-bit OS
+        // XXX: it's likely that this check is unnecessary and the comment is
+        // wrong because we no longer use PR_Realloc outside of NSPR and NSS.
+        size.value() > UINT32_MAX || size.value() > mTotal) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+
+    MOZ_DIAGNOSTIC_ASSERT(mFileData);
+    MOZ_RELEASE_ASSERT((mDataLen + aCount) <= mTotal);
+
+    nsresult rv = mAsyncStream->Read(mFileData + mDataLen, aCount, &bytesRead);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+  }
+
+  mDataLen += bytesRead;
+  return NS_OK;
+}
+
+// Helper methods
+
+void FileReader::ReadFileContent(Blob& aBlob, const nsAString& aCharset,
+                                 eDataFormat aDataFormat, ErrorResult& aRv) {
+  if (IsCurrentThreadRunningWorker() && !mWeakWorkerRef) {
+    // The worker is already shutting down.
+    return;
+  }
+
+  if (mReadyState == LOADING) {
+    aRv.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
+    return;
+  }
+
+  mError = nullptr;
+
+  SetDOMStringToNull(mResult);
+  mResultArrayBuffer = nullptr;
+
+  mAsyncStream = nullptr;
+
+  mTransferred = 0;
+  mTotal = 0;
+  mReadyState = EMPTY;
+  FreeFileData();
+
+  mBlob = &aBlob;
+  mDataFormat = aDataFormat;
+  CopyUTF16toUTF8(aCharset, mCharset);
+
+  {
+    nsCOMPtr<nsIInputStream> stream;
+    mBlob->CreateInputStream(getter_AddRefs(stream), aRv);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return;
+    }
+
+    aRv = NS_MakeAsyncNonBlockingInputStream(stream.forget(),
+                                             getter_AddRefs(mAsyncStream));
+    if (NS_WARN_IF(aRv.Failed())) {
+      return;
+    }
+  }
+
+  MOZ_ASSERT(mAsyncStream);
+
+  mTotal = mBlob->GetSize(aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  // Binary Format doesn't need a post-processing of the data. Everything is
+  // written directly into mResult.
+  if (mDataFormat != FILE_AS_BINARY) {
+    if (mDataFormat == FILE_AS_ARRAYBUFFER) {
+      mFileData = js_pod_malloc<char>(mTotal);
+    } else {
+      mFileData = (char*)malloc(mTotal);
+    }
+
+    if (!mFileData) {
+      NS_WARNING("Preallocation failed for ReadFileData");
+      aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+      return;
+    }
+  }
+
+  mAsyncWaitRunnable = new AsyncWaitRunnable(this);
+  aRv = NS_DispatchToCurrentThread(mAsyncWaitRunnable);
+  if (NS_WARN_IF(aRv.Failed())) {
+    FreeFileData();
+    return;
+  }
+
+  // FileReader should be in loading state here
+  mReadyState = LOADING;
+}
+
+void FileReader::InitialAsyncWait() {
+  mAsyncWaitRunnable = nullptr;
+
+  nsresult rv = DoAsyncWait();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    mReadyState = EMPTY;
+    FreeFileData();
+    return;
+  }
+
+  DispatchProgressEvent(nsLiteralString(LOADSTART_STR));
+}
+
+nsresult FileReader::GetAsText(Blob* aBlob, const nsACString& aCharset,
+                               const char* aFileData, uint32_t aDataLen,
+                               nsAString& aResult) {
+  // Try the API argument.
+  const Encoding* encoding = Encoding::ForLabel(aCharset);
+  if (!encoding) {
+    // API argument failed. Try the type property of the blob.
+    nsAutoString type16;
+    aBlob->GetType(type16);
+    NS_ConvertUTF16toUTF8 type(type16);
+    nsAutoCString specifiedCharset;
+    bool haveCharset;
+    int32_t charsetStart, charsetEnd;
+    NS_ExtractCharsetFromContentType(type, specifiedCharset, &haveCharset,
+                                     &charsetStart, &charsetEnd);
+    encoding = Encoding::ForLabel(specifiedCharset);
+    if (!encoding) {
+      // Type property failed. Use UTF-8.
+      encoding = UTF_8_ENCODING;
+    }
+  }
+
+  auto data = Span(reinterpret_cast<const uint8_t*>(aFileData), aDataLen);
+  nsresult rv;
+  std::tie(rv, std::ignore) = encoding->Decode(data, aResult);
+  return NS_FAILED(rv) ? rv : NS_OK;
+}
+
+nsresult FileReader::GetAsDataURL(Blob* aBlob, const char* aFileData,
+                                  uint32_t aDataLen, nsAString& aResult) {
+  aResult.AssignLiteral("data:");
+
+  nsAutoString contentType;
+  aBlob->GetType(contentType);
+  if (!contentType.IsEmpty()) {
+    aResult.Append(contentType);
+  } else {
+    aResult.AppendLiteral("application/octet-stream");
+  }
+  aResult.AppendLiteral(";base64,");
+
+  return Base64EncodeAppend(aFileData, aDataLen, aResult);
+}
+
+/* virtual */
+JSObject* FileReader::WrapObject(JSContext* aCx,
+                                 JS::Handle<JSObject*> aGivenProto) {
+  return FileReader_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+void FileReader::StartProgressEventTimer() {
+  if (!NS_IsMainThread() && !mWeakWorkerRef) {
+    // The worker is possibly shutting down if dispatching a DOM event right
+    // before this call triggered an InterruptCallback call.
+    // XXX Note, the check is limited to workers for now, since it is unclear
+    // in the spec how FileReader should behave in this case on the main thread.
+    return;
+  }
+
+  if (!mProgressNotifier) {
+    mProgressNotifier = NS_NewTimer(mTarget);
+  }
+
+  if (mProgressNotifier) {
+    mProgressEventWasDelayed = false;
+    mTimerIsActive = true;
+    mProgressNotifier->Cancel();
+    mProgressNotifier->InitWithCallback(this, NS_PROGRESS_EVENT_INTERVAL,
+                                        nsITimer::TYPE_ONE_SHOT);
+  }
+}
+
+void FileReader::ClearProgressEventTimer() {
+  mProgressEventWasDelayed = false;
+  mTimerIsActive = false;
+  if (mProgressNotifier) {
+    mProgressNotifier->Cancel();
+  }
+}
+
+void FileReader::FreeFileData() {
+  if (mFileData) {
+    if (mDataFormat == FILE_AS_ARRAYBUFFER) {
+      js_free(mFileData);
+    } else {
+      free(mFileData);
+    }
+    mFileData = nullptr;
+  }
+
+  mDataLen = 0;
+}
+
+void FileReader::FreeDataAndDispatchSuccess() {
+  FreeFileData();
+  mResult.SetIsVoid(false);
+  mAsyncStream = nullptr;
+  mBlob = nullptr;
+
+  // Dispatch event to signify end of a successful operation
+  DispatchProgressEvent(nsLiteralString(LOAD_STR));
+  DispatchProgressEvent(nsLiteralString(LOADEND_STR));
+}
+
+void FileReader::FreeDataAndDispatchError() {
+  MOZ_ASSERT(mError);
+
+  FreeFileData();
+  mResult.SetIsVoid(true);
+  mAsyncStream = nullptr;
+  mBlob = nullptr;
+
+  // Dispatch error event to signify load failure
+  DispatchProgressEvent(nsLiteralString(ERROR_STR));
+  DispatchProgressEvent(nsLiteralString(LOADEND_STR));
+}
+
+void FileReader::FreeDataAndDispatchError(nsresult aRv) {
+  // Set the status attribute, and dispatch the error event
+  switch (aRv) {
+    case NS_ERROR_FILE_NOT_FOUND:
+      mError = DOMException::Create(NS_ERROR_DOM_NOT_FOUND_ERR);
+      break;
+    case NS_ERROR_FILE_ACCESS_DENIED:
+      mError = DOMException::Create(NS_ERROR_DOM_SECURITY_ERR);
+      break;
+    default:
+      mError = DOMException::Create(NS_ERROR_DOM_FILE_NOT_READABLE_ERR);
+      break;
+  }
+
+  FreeDataAndDispatchError();
+}
+
+nsresult FileReader::DispatchProgressEvent(const nsAString& aType) {
+  ProgressEventInit init;
+  init.mBubbles = false;
+  init.mCancelable = false;
+  init.mLoaded = mTransferred;
+
+  if (mTotal != kUnknownSize) {
+    init.mLengthComputable = true;
+    init.mTotal = mTotal;
+  } else {
+    init.mLengthComputable = false;
+    init.mTotal = 0;
+  }
+  RefPtr<ProgressEvent> event = ProgressEvent::Constructor(this, aType, init);
+  event->SetTrusted(true);
+
+  ErrorResult rv;
+  DispatchEvent(*event, rv);
+  return rv.StealNSResult();
+}
+
+// nsITimerCallback
+NS_IMETHODIMP
+FileReader::Notify(nsITimer* aTimer) {
+  nsresult rv;
+  mTimerIsActive = false;
+
+  if (mProgressEventWasDelayed) {
+    rv = DispatchProgressEvent(u"progress"_ns);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    StartProgressEventTimer();
+  }
+
+  return NS_OK;
+}
+
+// InputStreamCallback
+NS_IMETHODIMP
+FileReader::OnInputStreamReady(nsIAsyncInputStream* aStream) {
+  // We use this class to decrease the busy counter at the end of this method.
+  // In theory we can do it immediatelly but, for debugging reasons, we want to
+  // be 100% sure we have a workerRef when OnLoadEnd() is called.
+  FileReaderDecreaseBusyCounter RAII(this);
+
+  if (mReadyState != LOADING || aStream != mAsyncStream) {
+    return NS_OK;
+  }
+
+  uint64_t count;
+  nsresult rv = aStream->Available(&count);
+
+  if (NS_SUCCEEDED(rv) && count) {
+    rv = DoReadData(count);
+
+    if (NS_SUCCEEDED(rv)) {
+      rv = DoAsyncWait();
+    }
+  }
+
+  if (NS_FAILED(rv) || !count) {
+    if (rv == NS_BASE_STREAM_CLOSED) {
+      rv = NS_OK;
+    }
+    OnLoadEnd(rv);
+    return NS_OK;
+  }
+
+  mTransferred += count;
+
+  // Notify the timer is the appropriate timeframe has passed
+  if (mTimerIsActive) {
+    mProgressEventWasDelayed = true;
+  } else {
+    rv = DispatchProgressEvent(nsLiteralString(PROGRESS_STR));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    StartProgressEventTimer();
+  }
+
+  return NS_OK;
+}
+
+// nsINamed
+NS_IMETHODIMP
+FileReader::GetName(nsACString& aName) {
+  aName.AssignLiteral("FileReader");
+  return NS_OK;
+}
+
+void FileReader::OnLoadEnd(nsresult aStatus) {
+  // Cancel the progress event timer
+  ClearProgressEventTimer();
+
+  // FileReader must be in DONE stage after an operation
+  mReadyState = DONE;
+
+  // Quick return, if failed.
+  if (NS_FAILED(aStatus)) {
+    FreeDataAndDispatchError(aStatus);
+    return;
+  }
+
+  // In case we read a different number of bytes, we can assume that the
+  // underlying storage has changed. We should not continue.
+  if (mDataLen != mTotal) {
+    FreeDataAndDispatchError(NS_ERROR_FAILURE);
+    return;
+  }
+
+  // ArrayBuffer needs a custom handling.
+  if (mDataFormat == FILE_AS_ARRAYBUFFER) {
+    OnLoadEndArrayBuffer();
+    return;
+  }
+
+  nsresult rv = NS_OK;
+
+  // We don't do anything special for Binary format.
+
+  if (mDataFormat == FILE_AS_DATAURL) {
+    rv = GetAsDataURL(mBlob, mFileData, mDataLen, mResult);
+  } else if (mDataFormat == FILE_AS_TEXT) {
+    if (!mFileData && mDataLen) {
+      rv = NS_ERROR_OUT_OF_MEMORY;
+    } else if (!mFileData) {
+      rv = GetAsText(mBlob, mCharset, "", mDataLen, mResult);
+    } else {
+      rv = GetAsText(mBlob, mCharset, mFileData, mDataLen, mResult);
+    }
+  }
+
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    FreeDataAndDispatchError(rv);
+    return;
+  }
+
+  FreeDataAndDispatchSuccess();
+}
+
+void FileReader::Abort() {
+  if (mReadyState == EMPTY || mReadyState == DONE) {
+    return;
+  }
+
+  MOZ_ASSERT(mReadyState == LOADING);
+
+  Cleanup();
+
+  // XXX The spec doesn't say this
+  mError = DOMException::Create(NS_ERROR_DOM_ABORT_ERR);
+
+  // Revert status and result attributes
+  SetDOMStringToNull(mResult);
+  mResultArrayBuffer = nullptr;
+
+  mBlob = nullptr;
+
+  // Dispatch the events
+  DispatchProgressEvent(nsLiteralString(ABORT_STR));
+  DispatchProgressEvent(nsLiteralString(LOADEND_STR));
+}
+
+nsresult FileReader::IncreaseBusyCounter() {
+  if (mWeakWorkerRef && mBusyCount++ == 0) {
+    if (NS_WARN_IF(!mWeakWorkerRef->GetPrivate())) {
+      return NS_ERROR_FAILURE;
+    }
+
+    RefPtr<FileReader> self = this;
+
+    RefPtr<StrongWorkerRef> ref =
+        StrongWorkerRef::Create(mWeakWorkerRef->GetPrivate(), "FileReader",
+                                [self]() { self->Shutdown(); });
+    if (NS_WARN_IF(!ref)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    mStrongWorkerRef = ref;
+  }
+
+  return NS_OK;
+}
+
+void FileReader::DecreaseBusyCounter() {
+  MOZ_ASSERT_IF(mStrongWorkerRef, mBusyCount);
+  if (mStrongWorkerRef && --mBusyCount == 0) {
+    mStrongWorkerRef = nullptr;
+  }
+}
+
+void FileReader::Cleanup() {
+  mReadyState = DONE;
+
+  if (mAsyncWaitRunnable) {
+    mAsyncWaitRunnable->Cancel();
+    mAsyncWaitRunnable = nullptr;
+  }
+
+  if (mAsyncStream) {
+    mAsyncStream->Close();
+    mAsyncStream = nullptr;
+  }
+
+  ClearProgressEventTimer();
+  FreeFileData();
+  mResultArrayBuffer = nullptr;
+}
+
+void FileReader::Shutdown() {
+  Cleanup();
+  if (mWeakWorkerRef) {
+    mWeakWorkerRef = nullptr;
+  }
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/FileReader.h b/dom/file/FileReader.h
new file mode 100644
index 0000000000..1c07b6193f
--- /dev/null
+++ b/dom/file/FileReader.h
@@ -0,0 +1,207 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_FileReader_h
+#define mozilla_dom_FileReader_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/DOMEventTargetHelper.h"
+
+#include "nsIAsyncInputStream.h"
+#include "nsIInterfaceRequestor.h"
+#include "nsINamed.h"
+#include "nsITimer.h"
+#include "nsCOMPtr.h"
+#include "nsString.h"
+#include "nsWeakReference.h"
+
+#define NS_PROGRESS_EVENT_INTERVAL 50
+
+class nsITimer;
+class nsIEventTarget;
+
+namespace mozilla::dom {
+
+class Blob;
+class DOMException;
+class OwningStringOrArrayBuffer;
+class StrongWorkerRef;
+class WeakWorkerRef;
+
+extern const uint64_t kUnknownSize;
+
+class FileReaderDecreaseBusyCounter;
+
+// 26a79031-c94b-47e9-850a-f04fe17bc026
+#define FILEREADER_ID                                \
+  {                                                  \
+    0x26a79031, 0xc94b, 0x47e9, {                    \
+      0x85, 0x0a, 0xf0, 0x4f, 0xe1, 0x7b, 0xc0, 0x26 \
+    }                                                \
+  }
+
+class FileReader final : public DOMEventTargetHelper,
+                         public nsIInterfaceRequestor,
+                         public nsSupportsWeakReference,
+                         public nsIInputStreamCallback,
+                         public nsITimerCallback,
+                         public nsINamed {
+  friend class FileReaderDecreaseBusyCounter;
+
+ public:
+  FileReader(nsIGlobalObject* aGlobal, WeakWorkerRef* aWorkerRef);
+
+  NS_DECL_ISUPPORTS_INHERITED
+
+  NS_DECL_NSITIMERCALLBACK
+  NS_DECL_NSIINPUTSTREAMCALLBACK
+  NS_DECL_NSIINTERFACEREQUESTOR
+  NS_DECL_NSINAMED
+
+  NS_DECLARE_STATIC_IID_ACCESSOR(FILEREADER_ID)
+
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_INHERITED(FileReader,
+                                                         DOMEventTargetHelper)
+
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+  // WebIDL
+  static already_AddRefed<FileReader> Constructor(const GlobalObject& aGlobal);
+  void ReadAsArrayBuffer(JSContext* aCx, Blob& aBlob, ErrorResult& aRv) {
+    ReadFileContent(aBlob, u""_ns, FILE_AS_ARRAYBUFFER, aRv);
+  }
+
+  void ReadAsText(Blob& aBlob, const Optional<nsAString>& aLabel,
+                  ErrorResult& aRv) {
+    if (aLabel.WasPassed()) {
+      ReadFileContent(aBlob, aLabel.Value(), FILE_AS_TEXT, aRv);
+    } else {
+      ReadFileContent(aBlob, u""_ns, FILE_AS_TEXT, aRv);
+    }
+  }
+
+  void ReadAsDataURL(Blob& aBlob, ErrorResult& aRv) {
+    ReadFileContent(aBlob, u""_ns, FILE_AS_DATAURL, aRv);
+  }
+
+  void Abort();
+
+  uint16_t ReadyState() const { return static_cast<uint16_t>(mReadyState); }
+
+  DOMException* GetError() const { return mError; }
+
+  void GetResult(JSContext* aCx, Nullable<OwningStringOrArrayBuffer>& aResult);
+
+  IMPL_EVENT_HANDLER(loadstart)
+  IMPL_EVENT_HANDLER(progress)
+  IMPL_EVENT_HANDLER(load)
+  IMPL_EVENT_HANDLER(abort)
+  IMPL_EVENT_HANDLER(error)
+  IMPL_EVENT_HANDLER(loadend)
+
+  void ReadAsBinaryString(Blob& aBlob, ErrorResult& aRv) {
+    ReadFileContent(aBlob, u""_ns, FILE_AS_BINARY, aRv);
+  }
+
+  enum eDataFormat {
+    FILE_AS_ARRAYBUFFER,
+    FILE_AS_BINARY,
+    FILE_AS_TEXT,
+    FILE_AS_DATAURL
+  };
+
+  eDataFormat DataFormat() const { return mDataFormat; }
+  const nsString& Result() const { return mResult; }
+
+  void InitialAsyncWait();
+
+ private:
+  ~FileReader() override;
+
+  // This must be in sync with dom/webidl/FileReader.webidl
+  enum eReadyState { EMPTY = 0, LOADING = 1, DONE = 2 };
+
+  void RootResultArrayBuffer();
+
+  void ReadFileContent(Blob& aBlob, const nsAString& aCharset,
+                       eDataFormat aDataFormat, ErrorResult& aRv);
+  nsresult GetAsText(Blob* aBlob, const nsACString& aCharset,
+                     const char* aFileData, uint32_t aDataLen,
+                     nsAString& aResult);
+  nsresult GetAsDataURL(Blob* aBlob, const char* aFileData, uint32_t aDataLen,
+                        nsAString& aResult);
+
+  void OnLoadEnd(nsresult aStatus);
+
+  void StartProgressEventTimer();
+  void ClearProgressEventTimer();
+
+  void FreeDataAndDispatchSuccess();
+  void FreeDataAndDispatchError();
+  void FreeDataAndDispatchError(nsresult aRv);
+  nsresult DispatchProgressEvent(const nsAString& aType);
+
+  nsresult DoAsyncWait();
+  nsresult DoReadData(uint64_t aCount);
+
+  void OnLoadEndArrayBuffer();
+
+  void FreeFileData();
+
+  nsresult IncreaseBusyCounter();
+  void DecreaseBusyCounter();
+
+  void Cleanup();
+  void Shutdown();
+
+  char* mFileData;
+  RefPtr<Blob> mBlob;
+  nsCString mCharset;
+  uint32_t mDataLen;
+
+  eDataFormat mDataFormat;
+
+  nsString mResult;
+
+  JS::Heap<JSObject*> mResultArrayBuffer;
+
+  nsCOMPtr<nsITimer> mProgressNotifier;
+  bool mProgressEventWasDelayed;
+  bool mTimerIsActive;
+
+  nsCOMPtr<nsIAsyncInputStream> mAsyncStream;
+
+  RefPtr<DOMException> mError;
+
+  eReadyState mReadyState;
+
+  uint64_t mTotal;
+  uint64_t mTransferred;
+
+  nsCOMPtr<nsIEventTarget> mTarget;
+
+  uint64_t mBusyCount;
+
+  // This is set if FileReader is created on workers, but it is null if the
+  // worker is shutting down. The null value is checked in ReadFileContent()
+  // before starting any reading.
+  RefPtr<WeakWorkerRef> mWeakWorkerRef;
+
+  // This value is set when the reading starts in order to keep the worker alive
+  // during the process.
+  RefPtr<StrongWorkerRef> mStrongWorkerRef;
+
+  // Runnable to start the reading asynchronous.
+  class AsyncWaitRunnable;
+  RefPtr<AsyncWaitRunnable> mAsyncWaitRunnable;
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(FileReader, FILEREADER_ID)
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_FileReader_h
diff --git a/dom/file/FileReaderSync.cpp b/dom/file/FileReaderSync.cpp
new file mode 100644
index 0000000000..e72d22b7c8
--- /dev/null
+++ b/dom/file/FileReaderSync.cpp
@@ -0,0 +1,489 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "FileReaderSync.h"
+
+#include "js/ArrayBuffer.h"  // JS::NewArrayBufferWithContents
+#include "js/RootingAPI.h"   // JS::{,Mutable}Handle
+#include "js/Utility.h"  // js::ArrayBufferContentsArena, JS::FreePolicy, js_pod_arena_malloc
+#include "mozilla/Unused.h"
+#include "mozilla/Base64.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/Encoding.h"
+#include "mozilla/dom/FileReaderSyncBinding.h"
+#include "nsCExternalHandlerService.h"
+#include "nsComponentManagerUtils.h"
+#include "nsCOMPtr.h"
+#include "nsError.h"
+#include "nsIConverterInputStream.h"
+#include "nsIInputStream.h"
+#include "nsIMultiplexInputStream.h"
+#include "nsStreamUtils.h"
+#include "nsStringStream.h"
+#include "nsISupportsImpl.h"
+#include "nsNetUtil.h"
+#include "nsServiceManagerUtils.h"
+#include "nsIAsyncInputStream.h"
+#include "mozilla/dom/WorkerPrivate.h"
+#include "mozilla/dom/WorkerRunnable.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+using mozilla::dom::GlobalObject;
+using mozilla::dom::Optional;
+
+// static
+already_AddRefed<FileReaderSync> FileReaderSync::Constructor(
+    const GlobalObject& aGlobal) {
+  RefPtr<FileReaderSync> frs = new FileReaderSync();
+
+  return frs.forget();
+}
+
+bool FileReaderSync::WrapObject(JSContext* aCx,
+                                JS::Handle<JSObject*> aGivenProto,
+                                JS::MutableHandle<JSObject*> aReflector) {
+  return FileReaderSync_Binding::Wrap(aCx, this, aGivenProto, aReflector);
+}
+
+void FileReaderSync::ReadAsArrayBuffer(JSContext* aCx,
+                                       JS::Handle<JSObject*> aScopeObj,
+                                       Blob& aBlob,
+                                       JS::MutableHandle<JSObject*> aRetval,
+                                       ErrorResult& aRv) {
+  uint64_t blobSize = aBlob.GetSize(aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  UniquePtr<char[], JS::FreePolicy> bufferData(
+      js_pod_arena_malloc<char>(js::ArrayBufferContentsArena, blobSize));
+  if (!bufferData) {
+    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+    return;
+  }
+
+  nsCOMPtr<nsIInputStream> stream;
+  aBlob.CreateInputStream(getter_AddRefs(stream), aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  uint32_t numRead;
+  aRv = SyncRead(stream, bufferData.get(), blobSize, &numRead);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  // The file is changed in the meantime?
+  if (numRead != blobSize) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return;
+  }
+
+  JSObject* arrayBuffer =
+      JS::NewArrayBufferWithContents(aCx, blobSize, bufferData.get());
+  if (!arrayBuffer) {
+    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+    return;
+  }
+  // arrayBuffer takes the ownership when it is not null. Otherwise we
+  // need to release it explicitly.
+  mozilla::Unused << bufferData.release();
+
+  aRetval.set(arrayBuffer);
+}
+
+void FileReaderSync::ReadAsBinaryString(Blob& aBlob, nsAString& aResult,
+                                        ErrorResult& aRv) {
+  nsCOMPtr<nsIInputStream> stream;
+  aBlob.CreateInputStream(getter_AddRefs(stream), aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  uint32_t numRead;
+  do {
+    char readBuf[4096];
+    aRv = SyncRead(stream, readBuf, sizeof(readBuf), &numRead);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return;
+    }
+
+    uint32_t oldLength = aResult.Length();
+    AppendASCIItoUTF16(Substring(readBuf, readBuf + numRead), aResult);
+    if (aResult.Length() - oldLength != numRead) {
+      aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+      return;
+    }
+  } while (numRead > 0);
+}
+
+void FileReaderSync::ReadAsText(Blob& aBlob,
+                                const Optional<nsAString>& aEncoding,
+                                nsAString& aResult, ErrorResult& aRv) {
+  nsCOMPtr<nsIInputStream> stream;
+  aBlob.CreateInputStream(getter_AddRefs(stream), aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  nsCString sniffBuf;
+  if (!sniffBuf.SetLength(3, fallible)) {
+    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+    return;
+  }
+
+  uint32_t numRead = 0;
+  aRv = SyncRead(stream, sniffBuf.BeginWriting(), sniffBuf.Length(), &numRead);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  // No data, we don't need to continue.
+  if (numRead == 0) {
+    aResult.Truncate();
+    return;
+  }
+
+  // Try the API argument.
+  const Encoding* encoding =
+      aEncoding.WasPassed() ? Encoding::ForLabel(aEncoding.Value()) : nullptr;
+  if (!encoding) {
+    // API argument failed. Try the type property of the blob.
+    nsAutoString type16;
+    aBlob.GetType(type16);
+    NS_ConvertUTF16toUTF8 type(type16);
+    nsAutoCString specifiedCharset;
+    bool haveCharset;
+    int32_t charsetStart, charsetEnd;
+    NS_ExtractCharsetFromContentType(type, specifiedCharset, &haveCharset,
+                                     &charsetStart, &charsetEnd);
+    encoding = Encoding::ForLabel(specifiedCharset);
+    if (!encoding) {
+      // Type property failed. Use UTF-8.
+      encoding = UTF_8_ENCODING;
+    }
+  }
+
+  if (numRead < sniffBuf.Length()) {
+    sniffBuf.Truncate(numRead);
+  }
+
+  // Let's recreate the full stream using a:
+  // multiplexStream(syncStream + original stream)
+  // In theory, we could try to see if the inputStream is a nsISeekableStream,
+  // but this doesn't work correctly for nsPipe3 - See bug 1349570.
+
+  nsCOMPtr<nsIMultiplexInputStream> multiplexStream =
+      do_CreateInstance("@mozilla.org/io/multiplex-input-stream;1");
+  if (NS_WARN_IF(!multiplexStream)) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return;
+  }
+
+  nsCOMPtr<nsIInputStream> sniffStringStream;
+  aRv = NS_NewCStringInputStream(getter_AddRefs(sniffStringStream), sniffBuf);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  aRv = multiplexStream->AppendStream(sniffStringStream);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  uint64_t blobSize = aBlob.GetSize(aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  nsCOMPtr<nsIInputStream> syncStream;
+  aRv = ConvertAsyncToSyncStream(blobSize - sniffBuf.Length(), stream.forget(),
+                                 getter_AddRefs(syncStream));
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  // ConvertAsyncToSyncStream returns a null syncStream if the stream has been
+  // already closed or there is nothing to read.
+  if (syncStream) {
+    aRv = multiplexStream->AppendStream(syncStream);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return;
+    }
+  }
+
+  nsAutoCString charset;
+  encoding->Name(charset);
+
+  nsCOMPtr<nsIInputStream> multiplex(do_QueryInterface(multiplexStream));
+  aRv = ConvertStream(multiplex, charset.get(), aResult);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+}
+
+void FileReaderSync::ReadAsDataURL(Blob& aBlob, nsAString& aResult,
+                                   ErrorResult& aRv) {
+  nsAutoString scratchResult;
+  scratchResult.AssignLiteral("data:");
+
+  nsString contentType;
+  aBlob.GetType(contentType);
+
+  if (contentType.IsEmpty()) {
+    scratchResult.AppendLiteral("application/octet-stream");
+  } else {
+    scratchResult.Append(contentType);
+  }
+  scratchResult.AppendLiteral(";base64,");
+
+  nsCOMPtr<nsIInputStream> stream;
+  aBlob.CreateInputStream(getter_AddRefs(stream), aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  uint64_t blobSize = aBlob.GetSize(aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  nsCOMPtr<nsIInputStream> syncStream;
+  aRv = ConvertAsyncToSyncStream(blobSize, stream.forget(),
+                                 getter_AddRefs(syncStream));
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  MOZ_ASSERT(syncStream);
+
+  uint64_t size;
+  aRv = syncStream->Available(&size);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  // The file is changed in the meantime?
+  if (blobSize != size) {
+    return;
+  }
+
+  nsAutoString encodedData;
+  aRv = Base64EncodeInputStream(syncStream, encodedData, size);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  scratchResult.Append(encodedData);
+
+  aResult = scratchResult;
+}
+
+nsresult FileReaderSync::ConvertStream(nsIInputStream* aStream,
+                                       const char* aCharset,
+                                       nsAString& aResult) {
+  nsCOMPtr<nsIConverterInputStream> converterStream =
+      do_CreateInstance("@mozilla.org/intl/converter-input-stream;1");
+  NS_ENSURE_TRUE(converterStream, NS_ERROR_FAILURE);
+
+  nsresult rv = converterStream->Init(
+      aStream, aCharset, 8192,
+      nsIConverterInputStream::DEFAULT_REPLACEMENT_CHARACTER);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIUnicharInputStream> unicharStream = converterStream;
+  NS_ENSURE_TRUE(unicharStream, NS_ERROR_FAILURE);
+
+  uint32_t numChars;
+  nsString result;
+  while (NS_SUCCEEDED(unicharStream->ReadString(8192, result, &numChars)) &&
+         numChars > 0) {
+    uint32_t oldLength = aResult.Length();
+    aResult.Append(result);
+    if (aResult.Length() - oldLength != result.Length()) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+  }
+
+  return rv;
+}
+
+namespace {
+
+// This runnable is used to terminate the sync event loop.
+class ReadReadyRunnable final : public WorkerSyncRunnable {
+ public:
+  ReadReadyRunnable(WorkerPrivate* aWorkerPrivate,
+                    nsIEventTarget* aSyncLoopTarget)
+      : WorkerSyncRunnable(aWorkerPrivate, aSyncLoopTarget) {}
+
+  bool WorkerRun(JSContext* aCx, WorkerPrivate* aWorkerPrivate) override {
+    aWorkerPrivate->AssertIsOnWorkerThread();
+    MOZ_ASSERT(mSyncLoopTarget);
+
+    nsCOMPtr<nsIEventTarget> syncLoopTarget;
+    mSyncLoopTarget.swap(syncLoopTarget);
+
+    aWorkerPrivate->StopSyncLoop(syncLoopTarget, NS_OK);
+    return true;
+  }
+
+ private:
+  ~ReadReadyRunnable() override = default;
+};
+
+// This class implements nsIInputStreamCallback and it will be called when the
+// stream is ready to be read.
+class ReadCallback final : public nsIInputStreamCallback {
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+
+  ReadCallback(WorkerPrivate* aWorkerPrivate, nsIEventTarget* aEventTarget)
+      : mWorkerPrivate(aWorkerPrivate), mEventTarget(aEventTarget) {}
+
+  NS_IMETHOD
+  OnInputStreamReady(nsIAsyncInputStream* aStream) override {
+    // I/O Thread. Now we need to block the sync event loop.
+    RefPtr<ReadReadyRunnable> runnable =
+        new ReadReadyRunnable(mWorkerPrivate, mEventTarget);
+    return mEventTarget->Dispatch(runnable.forget(), NS_DISPATCH_NORMAL);
+  }
+
+ private:
+  ~ReadCallback() = default;
+
+  // The worker is kept alive because of the sync event loop.
+  WorkerPrivate* mWorkerPrivate;
+  nsCOMPtr<nsIEventTarget> mEventTarget;
+};
+
+NS_IMPL_ADDREF(ReadCallback);
+NS_IMPL_RELEASE(ReadCallback);
+
+NS_INTERFACE_MAP_BEGIN(ReadCallback)
+  NS_INTERFACE_MAP_ENTRY(nsIInputStreamCallback)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIInputStreamCallback)
+NS_INTERFACE_MAP_END
+
+}  // namespace
+
+nsresult FileReaderSync::SyncRead(nsIInputStream* aStream, char* aBuffer,
+                                  uint32_t aBufferSize,
+                                  uint32_t* aTotalBytesRead) {
+  MOZ_ASSERT(aStream);
+  MOZ_ASSERT(aBuffer);
+  MOZ_ASSERT(aTotalBytesRead);
+
+  WorkerPrivate* workerPrivate = GetCurrentThreadWorkerPrivate();
+  MOZ_ASSERT(workerPrivate);
+
+  *aTotalBytesRead = 0;
+
+  nsCOMPtr<nsIAsyncInputStream> asyncStream;
+  nsCOMPtr<nsIEventTarget> target;
+
+  while (*aTotalBytesRead < aBufferSize) {
+    uint32_t currentBytesRead = 0;
+
+    // Let's read something.
+    nsresult rv =
+        aStream->Read(aBuffer + *aTotalBytesRead,
+                      aBufferSize - *aTotalBytesRead, &currentBytesRead);
+
+    // Nothing else to read.
+    if (rv == NS_BASE_STREAM_CLOSED ||
+        (NS_SUCCEEDED(rv) && currentBytesRead == 0)) {
+      return NS_OK;
+    }
+
+    // An error.
+    if (NS_FAILED(rv) && rv != NS_BASE_STREAM_WOULD_BLOCK) {
+      return rv;
+    }
+
+    // All good.
+    if (NS_SUCCEEDED(rv)) {
+      *aTotalBytesRead += currentBytesRead;
+      continue;
+    }
+
+    // We need to proceed async.
+    if (!asyncStream) {
+      asyncStream = do_QueryInterface(aStream);
+      if (!asyncStream) {
+        return rv;
+      }
+    }
+
+    AutoSyncLoopHolder syncLoop(workerPrivate, Canceling);
+
+    nsCOMPtr<nsISerialEventTarget> syncLoopTarget =
+        syncLoop.GetSerialEventTarget();
+    if (!syncLoopTarget) {
+      // SyncLoop creation can fail if the worker is shutting down.
+      return NS_ERROR_DOM_INVALID_STATE_ERR;
+    }
+
+    RefPtr<ReadCallback> callback =
+        new ReadCallback(workerPrivate, syncLoopTarget);
+
+    if (!target) {
+      target = do_GetService(NS_STREAMTRANSPORTSERVICE_CONTRACTID);
+      MOZ_ASSERT(target);
+    }
+
+    rv = asyncStream->AsyncWait(callback, 0, aBufferSize - *aTotalBytesRead,
+                                target);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    if (NS_WARN_IF(NS_FAILED(syncLoop.Run()))) {
+      return NS_ERROR_DOM_INVALID_STATE_ERR;
+    }
+  }
+
+  return NS_OK;
+}
+
+nsresult FileReaderSync::ConvertAsyncToSyncStream(
+    uint64_t aStreamSize, already_AddRefed<nsIInputStream> aAsyncStream,
+    nsIInputStream** aSyncStream) {
+  nsCOMPtr<nsIInputStream> asyncInputStream = std::move(aAsyncStream);
+
+  // If the stream is not async, we just need it to be bufferable.
+  nsCOMPtr<nsIAsyncInputStream> asyncStream =
+      do_QueryInterface(asyncInputStream);
+  if (!asyncStream) {
+    return NS_NewBufferedInputStream(aSyncStream, asyncInputStream.forget(),
+                                     4096);
+  }
+
+  nsAutoCString buffer;
+  if (!buffer.SetLength(aStreamSize, fallible)) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  uint32_t read;
+  nsresult rv =
+      SyncRead(asyncInputStream, buffer.BeginWriting(), aStreamSize, &read);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  if (read != aStreamSize) {
+    return NS_ERROR_FAILURE;
+  }
+
+  rv = NS_NewCStringInputStream(aSyncStream, std::move(buffer));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  return NS_OK;
+}
diff --git a/dom/file/FileReaderSync.h b/dom/file/FileReaderSync.h
new file mode 100644
index 0000000000..84eb5a73a8
--- /dev/null
+++ b/dom/file/FileReaderSync.h
@@ -0,0 +1,60 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_filereadersync_h__
+#define mozilla_dom_filereadersync_h__
+
+#include "mozilla/dom/WorkerCommon.h"
+#include "nsISupports.h"
+
+class nsIInputStream;
+
+namespace mozilla {
+class ErrorResult;
+
+namespace dom {
+class Blob;
+class GlobalObject;
+template <typename>
+class Optional;
+
+class FileReaderSync final {
+  NS_INLINE_DECL_REFCOUNTING(FileReaderSync)
+
+ private:
+  // Private destructor, to discourage deletion outside of Release():
+  ~FileReaderSync() = default;
+
+  nsresult ConvertStream(nsIInputStream* aStream, const char* aCharset,
+                         nsAString& aResult);
+
+  nsresult ConvertAsyncToSyncStream(
+      uint64_t aStreamSize, already_AddRefed<nsIInputStream> aAsyncStream,
+      nsIInputStream** aSyncStream);
+
+  nsresult SyncRead(nsIInputStream* aStream, char* aBuffer,
+                    uint32_t aBufferSize, uint32_t* aTotalBytesRead);
+
+ public:
+  static already_AddRefed<FileReaderSync> Constructor(
+      const GlobalObject& aGlobal);
+
+  bool WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto,
+                  JS::MutableHandle<JSObject*> aReflector);
+
+  void ReadAsArrayBuffer(JSContext* aCx, JS::Handle<JSObject*> aScopeObj,
+                         Blob& aBlob, JS::MutableHandle<JSObject*> aRetval,
+                         ErrorResult& aRv);
+  void ReadAsBinaryString(Blob& aBlob, nsAString& aResult, ErrorResult& aRv);
+  void ReadAsText(Blob& aBlob, const Optional<nsAString>& aEncoding,
+                  nsAString& aResult, ErrorResult& aRv);
+  void ReadAsDataURL(Blob& aBlob, nsAString& aResult, ErrorResult& aRv);
+};
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // mozilla_dom_filereadersync_h__
diff --git a/dom/file/MemoryBlobImpl.cpp b/dom/file/MemoryBlobImpl.cpp
new file mode 100644
index 0000000000..b6d5c442d1
--- /dev/null
+++ b/dom/file/MemoryBlobImpl.cpp
@@ -0,0 +1,168 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "MemoryBlobImpl.h"
+#include "mozilla/ipc/InputStreamUtils.h"
+#include "mozilla/IntegerPrintfMacros.h"
+#include "mozilla/SHA1.h"
+#include "nsIMemoryReporter.h"
+#include "nsPrintfCString.h"
+#include "nsRFPService.h"
+#include "nsStringStream.h"
+#include "prtime.h"
+
+namespace mozilla::dom {
+
+// static
+already_AddRefed<MemoryBlobImpl> MemoryBlobImpl::CreateWithCustomLastModified(
+    void* aMemoryBuffer, uint64_t aLength, const nsAString& aName,
+    const nsAString& aContentType, int64_t aLastModifiedDate) {
+  RefPtr<MemoryBlobImpl> blobImpl = new MemoryBlobImpl(
+      aMemoryBuffer, aLength, aName, aContentType, aLastModifiedDate);
+  return blobImpl.forget();
+}
+
+// static
+already_AddRefed<MemoryBlobImpl> MemoryBlobImpl::CreateWithLastModifiedNow(
+    void* aMemoryBuffer, uint64_t aLength, const nsAString& aName,
+    const nsAString& aContentType, RTPCallerType aRTPCallerType) {
+  int64_t lastModificationDate =
+      nsRFPService::ReduceTimePrecisionAsUSecs(PR_Now(), 0, aRTPCallerType);
+  return CreateWithCustomLastModified(aMemoryBuffer, aLength, aName,
+                                      aContentType, lastModificationDate);
+}
+
+nsresult MemoryBlobImpl::DataOwnerAdapter::Create(DataOwner* aDataOwner,
+                                                  size_t aStart, size_t aLength,
+                                                  nsIInputStream** _retval) {
+  MOZ_ASSERT(aDataOwner, "Uh ...");
+  Span data{static_cast<const char*>(aDataOwner->mData) + aStart, aLength};
+  RefPtr adapter = new MemoryBlobImpl::DataOwnerAdapter(aDataOwner, data);
+  return NS_NewByteInputStream(_retval, adapter);
+}
+
+already_AddRefed<BlobImpl> MemoryBlobImpl::CreateSlice(
+    uint64_t aStart, uint64_t aLength, const nsAString& aContentType,
+    ErrorResult& aRv) const {
+  RefPtr<BlobImpl> impl =
+      new MemoryBlobImpl(this, aStart, aLength, aContentType);
+  return impl.forget();
+}
+
+void MemoryBlobImpl::CreateInputStream(nsIInputStream** aStream,
+                                       ErrorResult& aRv) const {
+  if (mLength >= INT32_MAX) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return;
+  }
+
+  aRv = MemoryBlobImpl::DataOwnerAdapter::Create(mDataOwner, mStart, mLength,
+                                                 aStream);
+}
+
+/* static */
+StaticMutex MemoryBlobImpl::DataOwner::sDataOwnerMutex;
+
+/* static */ StaticAutoPtr<LinkedList<MemoryBlobImpl::DataOwner>>
+    MemoryBlobImpl::DataOwner::sDataOwners;
+
+/* static */
+bool MemoryBlobImpl::DataOwner::sMemoryReporterRegistered = false;
+
+MOZ_DEFINE_MALLOC_SIZE_OF(MemoryFileDataOwnerMallocSizeOf)
+
+class MemoryBlobImplDataOwnerMemoryReporter final : public nsIMemoryReporter {
+  ~MemoryBlobImplDataOwnerMemoryReporter() = default;
+
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+
+  NS_IMETHOD CollectReports(nsIHandleReportCallback* aHandleReport,
+                            nsISupports* aData, bool aAnonymize) override {
+    using DataOwner = MemoryBlobImpl::DataOwner;
+
+    StaticMutexAutoLock lock(DataOwner::sDataOwnerMutex);
+
+    if (!DataOwner::sDataOwners) {
+      return NS_OK;
+    }
+
+    const size_t LARGE_OBJECT_MIN_SIZE = 8 * 1024;
+    size_t smallObjectsTotal = 0;
+
+    for (DataOwner* owner = DataOwner::sDataOwners->getFirst(); owner;
+         owner = owner->getNext()) {
+      size_t size = MemoryFileDataOwnerMallocSizeOf(owner->mData);
+
+      if (size < LARGE_OBJECT_MIN_SIZE) {
+        smallObjectsTotal += size;
+      } else {
+        SHA1Sum sha1;
+        sha1.update(owner->mData, owner->mLength);
+        uint8_t digest[SHA1Sum::kHashSize];  // SHA1 digests are 20 bytes long.
+        sha1.finish(digest);
+
+        nsAutoCString digestString;
+        for (size_t i = 0; i < sizeof(digest); i++) {
+          digestString.AppendPrintf("%02x", digest[i]);
+        }
+
+        aHandleReport->Callback(
+            /* process */ ""_ns,
+            nsPrintfCString(
+                "explicit/dom/memory-file-data/large/file(length=%" PRIu64
+                ", sha1=%s)",
+                owner->mLength,
+                aAnonymize ? "<anonymized>" : digestString.get()),
+            KIND_HEAP, UNITS_BYTES, size,
+            nsPrintfCString(
+                "Memory used to back a memory file of length %" PRIu64
+                " bytes.  The file "
+                "has a sha1 of %s.\n\n"
+                "Note that the allocator may round up a memory file's length "
+                "-- "
+                "that is, an N-byte memory file may take up more than N bytes "
+                "of "
+                "memory.",
+                owner->mLength, digestString.get()),
+            aData);
+      }
+    }
+
+    if (smallObjectsTotal > 0) {
+      aHandleReport->Callback(
+          /* process */ ""_ns, "explicit/dom/memory-file-data/small"_ns,
+          KIND_HEAP, UNITS_BYTES, smallObjectsTotal,
+          nsPrintfCString(
+              "Memory used to back small memory files (i.e. those taking up "
+              "less "
+              "than %zu bytes of memory each).\n\n"
+              "Note that the allocator may round up a memory file's length -- "
+              "that is, an N-byte memory file may take up more than N bytes of "
+              "memory.",
+              LARGE_OBJECT_MIN_SIZE),
+          aData);
+    }
+
+    return NS_OK;
+  }
+};
+
+NS_IMPL_ISUPPORTS(MemoryBlobImplDataOwnerMemoryReporter, nsIMemoryReporter)
+
+/* static */
+void MemoryBlobImpl::DataOwner::EnsureMemoryReporterRegistered() {
+  sDataOwnerMutex.AssertCurrentThreadOwns();
+  if (sMemoryReporterRegistered) {
+    return;
+  }
+
+  RegisterStrongMemoryReporter(new MemoryBlobImplDataOwnerMemoryReporter());
+
+  sMemoryReporterRegistered = true;
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/MemoryBlobImpl.h b/dom/file/MemoryBlobImpl.h
new file mode 100644
index 0000000000..29d812feee
--- /dev/null
+++ b/dom/file/MemoryBlobImpl.h
@@ -0,0 +1,160 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_MemoryBlobImpl_h
+#define mozilla_dom_MemoryBlobImpl_h
+
+#include "mozilla/dom/BaseBlobImpl.h"
+#include "mozilla/LinkedList.h"
+#include "mozilla/StaticMutex.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/StreamBufferSource.h"
+#include "nsCOMPtr.h"
+#include "nsICloneableInputStream.h"
+#include "nsIInputStream.h"
+#include "nsIIPCSerializableInputStream.h"
+#include "nsISeekableStream.h"
+
+namespace mozilla::dom {
+
+class MemoryBlobImpl final : public BaseBlobImpl {
+ public:
+  NS_INLINE_DECL_REFCOUNTING_INHERITED(MemoryBlobImpl, BaseBlobImpl)
+
+  // File constructor.
+  static already_AddRefed<MemoryBlobImpl> CreateWithLastModifiedNow(
+      void* aMemoryBuffer, uint64_t aLength, const nsAString& aName,
+      const nsAString& aContentType, RTPCallerType aRTPCallerType);
+
+  // File constructor with custom lastModified attribue value. You should
+  // probably use CreateWithLastModifiedNow() instead of this one.
+  static already_AddRefed<MemoryBlobImpl> CreateWithCustomLastModified(
+      void* aMemoryBuffer, uint64_t aLength, const nsAString& aName,
+      const nsAString& aContentType, int64_t aLastModifiedDate);
+
+  // Blob constructor.
+  MemoryBlobImpl(void* aMemoryBuffer, uint64_t aLength,
+                 const nsAString& aContentType)
+      : BaseBlobImpl(aContentType, aLength),
+        mDataOwner(new DataOwner(aMemoryBuffer, aLength)) {
+    MOZ_ASSERT(mDataOwner && mDataOwner->mData, "must have data");
+  }
+
+  void CreateInputStream(nsIInputStream** aStream,
+                         ErrorResult& aRv) const override;
+
+  already_AddRefed<BlobImpl> CreateSlice(uint64_t aStart, uint64_t aLength,
+                                         const nsAString& aContentType,
+                                         ErrorResult& aRv) const override;
+
+  bool IsMemoryFile() const override { return true; }
+
+  size_t GetAllocationSize() const override { return mLength; }
+
+  size_t GetAllocationSize(
+      FallibleTArray<BlobImpl*>& aVisitedBlobImpls) const override {
+    return GetAllocationSize();
+  }
+
+  void GetBlobImplType(nsAString& aBlobImplType) const override {
+    aBlobImplType = u"MemoryBlobImpl"_ns;
+  }
+
+  class DataOwner final : public mozilla::LinkedListElement<DataOwner> {
+   public:
+    NS_INLINE_DECL_THREADSAFE_REFCOUNTING(DataOwner)
+    DataOwner(void* aMemoryBuffer, uint64_t aLength)
+        : mData(aMemoryBuffer), mLength(aLength) {
+      mozilla::StaticMutexAutoLock lock(sDataOwnerMutex);
+
+      if (!sDataOwners) {
+        sDataOwners = new mozilla::LinkedList<DataOwner>();
+        EnsureMemoryReporterRegistered();
+      }
+      sDataOwners->insertBack(this);
+    }
+
+   private:
+    // Private destructor, to discourage deletion outside of Release():
+    ~DataOwner() {
+      mozilla::StaticMutexAutoLock lock(sDataOwnerMutex);
+
+      remove();
+      if (sDataOwners->isEmpty()) {
+        // Free the linked list if it's empty.
+        sDataOwners = nullptr;
+      }
+
+      free(mData);
+    }
+
+   public:
+    static void EnsureMemoryReporterRegistered();
+
+    // sDataOwners and sMemoryReporterRegistered may only be accessed while
+    // holding sDataOwnerMutex!  You also must hold the mutex while touching
+    // elements of the linked list that DataOwner inherits from.
+    static mozilla::StaticMutex sDataOwnerMutex MOZ_UNANNOTATED;
+    static mozilla::StaticAutoPtr<mozilla::LinkedList<DataOwner> > sDataOwners;
+    static bool sMemoryReporterRegistered;
+
+    void* mData;
+    uint64_t mLength;
+  };
+
+  class DataOwnerAdapter final : public StreamBufferSource {
+    using DataOwner = MemoryBlobImpl::DataOwner;
+
+   public:
+    static nsresult Create(DataOwner* aDataOwner, size_t aStart, size_t aLength,
+                           nsIInputStream** _retval);
+
+    Span<const char> Data() override { return mData; }
+
+    // This StreamBufferSource is owning, as the `mData` span references the
+    // immutable data buffer owned by `mDataOwner` which is being kept alive.
+    bool Owning() override { return true; }
+
+    // The memory usage from `DataOwner` is reported elsewhere, so we don't need
+    // to record it here.
+    size_t SizeOfExcludingThisEvenIfShared(MallocSizeOf) override { return 0; }
+
+   private:
+    ~DataOwnerAdapter() override = default;
+
+    DataOwnerAdapter(DataOwner* aDataOwner, Span<const char> aData)
+        : mDataOwner(aDataOwner), mData(aData) {}
+
+    RefPtr<DataOwner> mDataOwner;
+    Span<const char> mData;
+  };
+
+ private:
+  // File constructor.
+  MemoryBlobImpl(void* aMemoryBuffer, uint64_t aLength, const nsAString& aName,
+                 const nsAString& aContentType, int64_t aLastModifiedDate)
+      : BaseBlobImpl(aName, aContentType, aLength, aLastModifiedDate),
+        mDataOwner(new DataOwner(aMemoryBuffer, aLength)) {
+    MOZ_ASSERT(mDataOwner && mDataOwner->mData, "must have data");
+  }
+
+  // Create slice
+  MemoryBlobImpl(const MemoryBlobImpl* aOther, uint64_t aStart,
+                 uint64_t aLength, const nsAString& aContentType)
+      : BaseBlobImpl(aContentType, aOther->mStart + aStart, aLength),
+        mDataOwner(aOther->mDataOwner) {
+    MOZ_ASSERT(mDataOwner && mDataOwner->mData, "must have data");
+  }
+
+  ~MemoryBlobImpl() override = default;
+
+  // Used when backed by a memory store
+  RefPtr<DataOwner> mDataOwner;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_MemoryBlobImpl_h
diff --git a/dom/file/MultipartBlobImpl.cpp b/dom/file/MultipartBlobImpl.cpp
new file mode 100644
index 0000000000..b795793aef
--- /dev/null
+++ b/dom/file/MultipartBlobImpl.cpp
@@ -0,0 +1,338 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "MultipartBlobImpl.h"
+#include "jsfriendapi.h"
+#include "mozilla/dom/BlobSet.h"
+#include "mozilla/dom/FileBinding.h"
+#include "mozilla/dom/UnionTypes.h"
+#include "nsComponentManagerUtils.h"
+#include "nsIGlobalObject.h"
+#include "nsIMultiplexInputStream.h"
+#include "nsReadableUtils.h"
+#include "nsRFPService.h"
+#include "nsStringStream.h"
+#include "nsTArray.h"
+#include "nsJSUtils.h"
+#include "nsContentUtils.h"
+#include <algorithm>
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+/* static */
+already_AddRefed<MultipartBlobImpl> MultipartBlobImpl::Create(
+    nsTArray<RefPtr<BlobImpl>>&& aBlobImpls, const nsAString& aName,
+    const nsAString& aContentType, RTPCallerType aRTPCallerType,
+    ErrorResult& aRv) {
+  RefPtr<MultipartBlobImpl> blobImpl =
+      new MultipartBlobImpl(std::move(aBlobImpls), aName, aContentType);
+  blobImpl->SetLengthAndModifiedDate(Some(aRTPCallerType), aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  return blobImpl.forget();
+}
+
+/* static */
+already_AddRefed<MultipartBlobImpl> MultipartBlobImpl::Create(
+    nsTArray<RefPtr<BlobImpl>>&& aBlobImpls, const nsAString& aContentType,
+    ErrorResult& aRv) {
+  RefPtr<MultipartBlobImpl> blobImpl =
+      new MultipartBlobImpl(std::move(aBlobImpls), aContentType);
+  blobImpl->SetLengthAndModifiedDate(/* aRTPCallerType */ Nothing(), aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  return blobImpl.forget();
+}
+
+void MultipartBlobImpl::CreateInputStream(nsIInputStream** aStream,
+                                          ErrorResult& aRv) const {
+  *aStream = nullptr;
+
+  uint32_t length = mBlobImpls.Length();
+  if (length == 0 || mLength == 0) {
+    aRv = NS_NewCStringInputStream(aStream, ""_ns);
+    return;
+  }
+
+  if (length == 1) {
+    BlobImpl* blobImpl = mBlobImpls.ElementAt(0);
+    blobImpl->CreateInputStream(aStream, aRv);
+    return;
+  }
+
+  nsCOMPtr<nsIMultiplexInputStream> stream =
+      do_CreateInstance("@mozilla.org/io/multiplex-input-stream;1");
+  if (NS_WARN_IF(!stream)) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return;
+  }
+
+  uint32_t i;
+  for (i = 0; i < length; i++) {
+    nsCOMPtr<nsIInputStream> scratchStream;
+    BlobImpl* blobImpl = mBlobImpls.ElementAt(i).get();
+
+    // nsIMultiplexInputStream doesn't work well with empty sub streams. Let's
+    // skip the empty blobs.
+    uint32_t size = blobImpl->GetSize(aRv);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return;
+    }
+
+    if (size == 0) {
+      continue;
+    }
+
+    blobImpl->CreateInputStream(getter_AddRefs(scratchStream), aRv);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return;
+    }
+
+    aRv = stream->AppendStream(scratchStream);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return;
+    }
+  }
+
+  CallQueryInterface(stream, aStream);
+}
+
+already_AddRefed<BlobImpl> MultipartBlobImpl::CreateSlice(
+    uint64_t aStart, uint64_t aLength, const nsAString& aContentType,
+    ErrorResult& aRv) const {
+  // If we clamped to nothing we create an empty blob
+  nsTArray<RefPtr<BlobImpl>> blobImpls;
+
+  uint64_t length = aLength;
+  uint64_t skipStart = aStart;
+
+  // Prune the list of blobs if we can
+  uint32_t i;
+  for (i = 0; length && skipStart && i < mBlobImpls.Length(); i++) {
+    BlobImpl* blobImpl = mBlobImpls[i].get();
+
+    uint64_t l = blobImpl->GetSize(aRv);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return nullptr;
+    }
+
+    if (skipStart < l) {
+      uint64_t upperBound = std::min<uint64_t>(l - skipStart, length);
+
+      RefPtr<BlobImpl> firstBlobImpl =
+          blobImpl->CreateSlice(skipStart, upperBound, aContentType, aRv);
+      if (NS_WARN_IF(aRv.Failed())) {
+        return nullptr;
+      }
+
+      // Avoid wrapping a single blob inside an MultipartBlobImpl
+      if (length == upperBound) {
+        return firstBlobImpl.forget();
+      }
+
+      blobImpls.AppendElement(firstBlobImpl);
+      length -= upperBound;
+      i++;
+      break;
+    }
+    skipStart -= l;
+  }
+
+  // Now append enough blobs until we're done
+  for (; length && i < mBlobImpls.Length(); i++) {
+    BlobImpl* blobImpl = mBlobImpls[i].get();
+
+    uint64_t l = blobImpl->GetSize(aRv);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return nullptr;
+    }
+
+    if (length < l) {
+      RefPtr<BlobImpl> lastBlobImpl =
+          blobImpl->CreateSlice(0, length, aContentType, aRv);
+      if (NS_WARN_IF(aRv.Failed())) {
+        return nullptr;
+      }
+
+      blobImpls.AppendElement(lastBlobImpl);
+    } else {
+      blobImpls.AppendElement(blobImpl);
+    }
+    length -= std::min<uint64_t>(l, length);
+  }
+
+  // we can create our blob now
+  RefPtr<BlobImpl> impl = Create(std::move(blobImpls), aContentType, aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  return impl.forget();
+}
+
+void MultipartBlobImpl::InitializeBlob(RTPCallerType aRTPCallerType,
+                                       ErrorResult& aRv) {
+  SetLengthAndModifiedDate(Some(aRTPCallerType), aRv);
+  NS_WARNING_ASSERTION(!aRv.Failed(), "SetLengthAndModifiedDate failed");
+}
+
+void MultipartBlobImpl::InitializeBlob(const Sequence<Blob::BlobPart>& aData,
+                                       const nsAString& aContentType,
+                                       bool aNativeEOL,
+                                       RTPCallerType aRTPCallerType,
+                                       ErrorResult& aRv) {
+  mContentType = aContentType;
+  BlobSet blobSet;
+
+  for (uint32_t i = 0, len = aData.Length(); i < len; ++i) {
+    const Blob::BlobPart& data = aData[i];
+
+    if (data.IsBlob()) {
+      RefPtr<Blob> blob = data.GetAsBlob().get();
+      aRv = blobSet.AppendBlobImpl(blob->Impl());
+      if (aRv.Failed()) {
+        return;
+      }
+    }
+
+    else if (data.IsUTF8String()) {
+      aRv = blobSet.AppendUTF8String(data.GetAsUTF8String(), aNativeEOL);
+      if (aRv.Failed()) {
+        return;
+      }
+    }
+
+    else if (data.IsArrayBuffer()) {
+      const ArrayBuffer& buffer = data.GetAsArrayBuffer();
+      buffer.ComputeState();
+      aRv = blobSet.AppendVoidPtr(buffer.Data(), buffer.Length());
+      if (aRv.Failed()) {
+        return;
+      }
+    }
+
+    else if (data.IsArrayBufferView()) {
+      const ArrayBufferView& buffer = data.GetAsArrayBufferView();
+      buffer.ComputeState();
+      aRv = blobSet.AppendVoidPtr(buffer.Data(), buffer.Length());
+      if (aRv.Failed()) {
+        return;
+      }
+    }
+
+    else {
+      MOZ_CRASH("Impossible blob data type.");
+    }
+  }
+
+  mBlobImpls = blobSet.GetBlobImpls();
+  SetLengthAndModifiedDate(Some(aRTPCallerType), aRv);
+  NS_WARNING_ASSERTION(!aRv.Failed(), "SetLengthAndModifiedDate failed");
+}
+
+void MultipartBlobImpl::SetLengthAndModifiedDate(
+    const Maybe<RTPCallerType>& aRTPCallerType, ErrorResult& aRv) {
+  MOZ_ASSERT(mLength == MULTIPARTBLOBIMPL_UNKNOWN_LENGTH);
+  MOZ_ASSERT_IF(mIsFile, IsLastModificationDateUnset());
+
+  uint64_t totalLength = 0;
+  int64_t lastModified = 0;
+  bool lastModifiedSet = false;
+
+  for (uint32_t index = 0, count = mBlobImpls.Length(); index < count;
+       index++) {
+    RefPtr<BlobImpl>& blob = mBlobImpls[index];
+
+    uint64_t subBlobLength = blob->GetSize(aRv);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return;
+    }
+
+    MOZ_ASSERT(UINT64_MAX - subBlobLength >= totalLength);
+    totalLength += subBlobLength;
+
+    if (blob->IsFile()) {
+      int64_t partLastModified = blob->GetLastModified(aRv);
+      if (NS_WARN_IF(aRv.Failed())) {
+        return;
+      }
+
+      if (lastModified < partLastModified) {
+        lastModified = partLastModified * PR_USEC_PER_MSEC;
+        lastModifiedSet = true;
+      }
+    }
+  }
+
+  mLength = totalLength;
+
+  if (mIsFile) {
+    if (lastModifiedSet) {
+      SetLastModificationDatePrecisely(lastModified);
+    } else {
+      MOZ_ASSERT(aRTPCallerType.isSome());
+
+      // We cannot use PR_Now() because bug 493756 and, for this reason:
+      //   var x = new Date(); var f = new File(...);
+      //   x.getTime() < f.dateModified.getTime()
+      // could fail.
+      SetLastModificationDate(aRTPCallerType.value(), JS_Now());
+    }
+  }
+}
+
+size_t MultipartBlobImpl::GetAllocationSize() const {
+  FallibleTArray<BlobImpl*> visitedBlobs;
+
+  // We want to report the unique blob allocation, avoiding duplicated blobs in
+  // the multipart blob tree.
+  size_t total = 0;
+  for (uint32_t i = 0; i < mBlobImpls.Length(); ++i) {
+    total += mBlobImpls[i]->GetAllocationSize(visitedBlobs);
+  }
+
+  return total;
+}
+
+size_t MultipartBlobImpl::GetAllocationSize(
+    FallibleTArray<BlobImpl*>& aVisitedBlobs) const {
+  FallibleTArray<BlobImpl*> visitedBlobs;
+
+  size_t total = 0;
+  for (BlobImpl* blobImpl : mBlobImpls) {
+    if (!aVisitedBlobs.Contains(blobImpl)) {
+      if (NS_WARN_IF(!aVisitedBlobs.AppendElement(blobImpl, fallible))) {
+        return 0;
+      }
+      total += blobImpl->GetAllocationSize(aVisitedBlobs);
+    }
+  }
+
+  return total;
+}
+
+void MultipartBlobImpl::GetBlobImplType(nsAString& aBlobImplType) const {
+  aBlobImplType.AssignLiteral("MultipartBlobImpl[");
+
+  StringJoinAppend(aBlobImplType, u", "_ns, mBlobImpls,
+                   [](nsAString& dest, BlobImpl* subBlobImpl) {
+                     nsAutoString blobImplType;
+                     subBlobImpl->GetBlobImplType(blobImplType);
+
+                     dest.Append(blobImplType);
+                   });
+
+  aBlobImplType.AppendLiteral("]");
+}
+
+void MultipartBlobImpl::SetLastModified(int64_t aLastModified) {
+  SetLastModificationDatePrecisely(aLastModified * PR_USEC_PER_MSEC);
+}
diff --git a/dom/file/MultipartBlobImpl.h b/dom/file/MultipartBlobImpl.h
new file mode 100644
index 0000000000..cb62f2adb5
--- /dev/null
+++ b/dom/file/MultipartBlobImpl.h
@@ -0,0 +1,106 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_MultipartBlobImpl_h
+#define mozilla_dom_MultipartBlobImpl_h
+
+#include <utility>
+
+#include "Blob.h"
+#include "nsContentUtils.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/dom/BaseBlobImpl.h"
+
+namespace mozilla {
+class ErrorResult;
+
+namespace dom {
+
+// This is just a sentinel value to be sure that we don't call
+// SetLengthAndModifiedDate more than once.
+constexpr int64_t MULTIPARTBLOBIMPL_UNKNOWN_LAST_MODIFIED = INT64_MAX;
+constexpr uint64_t MULTIPARTBLOBIMPL_UNKNOWN_LENGTH = UINT64_MAX;
+
+class MultipartBlobImpl final : public BaseBlobImpl {
+ public:
+  NS_INLINE_DECL_REFCOUNTING_INHERITED(MultipartBlobImpl, BaseBlobImpl)
+
+  // Create as a file
+  static already_AddRefed<MultipartBlobImpl> Create(
+      nsTArray<RefPtr<BlobImpl>>&& aBlobImpls, const nsAString& aName,
+      const nsAString& aContentType, RTPCallerType aRTPCallerType,
+      ErrorResult& aRv);
+
+  // Create as a blob
+  static already_AddRefed<MultipartBlobImpl> Create(
+      nsTArray<RefPtr<BlobImpl>>&& aBlobImpls, const nsAString& aContentType,
+      ErrorResult& aRv);
+
+  // Create as a file to be later initialized
+  explicit MultipartBlobImpl(const nsAString& aName)
+      : BaseBlobImpl(aName, u""_ns, MULTIPARTBLOBIMPL_UNKNOWN_LENGTH,
+                     MULTIPARTBLOBIMPL_UNKNOWN_LAST_MODIFIED) {}
+
+  // Create as a blob to be later initialized
+  MultipartBlobImpl()
+      : BaseBlobImpl(u""_ns, MULTIPARTBLOBIMPL_UNKNOWN_LENGTH) {}
+
+  void InitializeBlob(RTPCallerType aRTPCallerType, ErrorResult& aRv);
+
+  void InitializeBlob(const Sequence<Blob::BlobPart>& aData,
+                      const nsAString& aContentType, bool aNativeEOL,
+                      RTPCallerType aRTPCallerType, ErrorResult& aRv);
+
+  already_AddRefed<BlobImpl> CreateSlice(uint64_t aStart, uint64_t aLength,
+                                         const nsAString& aContentType,
+                                         ErrorResult& aRv) const override;
+
+  uint64_t GetSize(ErrorResult& aRv) override { return mLength; }
+
+  void CreateInputStream(nsIInputStream** aStream,
+                         ErrorResult& aRv) const override;
+
+  const nsTArray<RefPtr<BlobImpl>>* GetSubBlobImpls() const override {
+    return mBlobImpls.Length() ? &mBlobImpls : nullptr;
+  }
+
+  void SetName(const nsAString& aName) { mName = aName; }
+
+  size_t GetAllocationSize() const override;
+  size_t GetAllocationSize(
+      FallibleTArray<BlobImpl*>& aVisitedBlobs) const override;
+
+  void GetBlobImplType(nsAString& aBlobImplType) const override;
+
+  void SetLastModified(int64_t aLastModified);
+
+ protected:
+  // File constructor.
+  MultipartBlobImpl(nsTArray<RefPtr<BlobImpl>>&& aBlobImpls,
+                    const nsAString& aName, const nsAString& aContentType)
+      : BaseBlobImpl(aName, aContentType, MULTIPARTBLOBIMPL_UNKNOWN_LENGTH,
+                     MULTIPARTBLOBIMPL_UNKNOWN_LAST_MODIFIED),
+        mBlobImpls(std::move(aBlobImpls)) {}
+
+  // Blob constructor.
+  MultipartBlobImpl(nsTArray<RefPtr<BlobImpl>>&& aBlobImpls,
+                    const nsAString& aContentType)
+      : BaseBlobImpl(aContentType, MULTIPARTBLOBIMPL_UNKNOWN_LENGTH),
+        mBlobImpls(std::move(aBlobImpls)) {}
+
+  ~MultipartBlobImpl() override = default;
+
+  void SetLengthAndModifiedDate(const Maybe<RTPCallerType>& aRTPCallerType,
+                                ErrorResult& aRv);
+
+  nsTArray<RefPtr<BlobImpl>> mBlobImpls;
+};
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // mozilla_dom_MultipartBlobImpl_h
diff --git a/dom/file/MutableBlobStorage.cpp b/dom/file/MutableBlobStorage.cpp
new file mode 100644
index 0000000000..3bb1a4f169
--- /dev/null
+++ b/dom/file/MutableBlobStorage.cpp
@@ -0,0 +1,667 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "EmptyBlobImpl.h"
+#include "MutableBlobStorage.h"
+#include "MemoryBlobImpl.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/dom/TemporaryIPCBlobChild.h"
+#include "mozilla/dom/WorkerPrivate.h"
+#include "mozilla/ipc/BackgroundChild.h"
+#include "mozilla/ipc/PBackgroundChild.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/TaskQueue.h"
+#include "File.h"
+#include "nsAnonymousTemporaryFile.h"
+#include "nsNetCID.h"
+#include "nsProxyRelease.h"
+
+#define BLOB_MEMORY_TEMPORARY_FILE 1048576
+
+namespace mozilla::dom {
+
+namespace {
+
+// This class uses the callback to inform when the Blob is created or when the
+// error must be propagated.
+class BlobCreationDoneRunnable final : public Runnable {
+ public:
+  BlobCreationDoneRunnable(MutableBlobStorage* aBlobStorage,
+                           MutableBlobStorageCallback* aCallback,
+                           BlobImpl* aBlobImpl, nsresult aRv)
+      : Runnable("dom::BlobCreationDoneRunnable"),
+        mBlobStorage(aBlobStorage),
+        mCallback(aCallback),
+        mBlobImpl(aBlobImpl),
+        mRv(aRv) {
+    MOZ_ASSERT(aBlobStorage);
+    MOZ_ASSERT(aCallback);
+    MOZ_ASSERT((NS_FAILED(aRv) && !aBlobImpl) ||
+               (NS_SUCCEEDED(aRv) && aBlobImpl));
+  }
+
+  NS_IMETHOD
+  Run() override {
+    MOZ_ASSERT(NS_IsMainThread());
+    MOZ_ASSERT(mBlobStorage);
+    mCallback->BlobStoreCompleted(mBlobStorage, mBlobImpl, mRv);
+    mCallback = nullptr;
+    mBlobImpl = nullptr;
+    return NS_OK;
+  }
+
+ private:
+  ~BlobCreationDoneRunnable() override {
+    MOZ_ASSERT(mBlobStorage);
+    // If something when wrong, we still have to release these objects in the
+    // correct thread.
+    NS_ProxyRelease("BlobCreationDoneRunnable::mCallback",
+                    mBlobStorage->EventTarget(), mCallback.forget());
+  }
+
+  RefPtr<MutableBlobStorage> mBlobStorage;
+  RefPtr<MutableBlobStorageCallback> mCallback;
+  RefPtr<BlobImpl> mBlobImpl;
+  nsresult mRv;
+};
+
+// Simple runnable to propagate the error to the BlobStorage.
+class ErrorPropagationRunnable final : public Runnable {
+ public:
+  ErrorPropagationRunnable(MutableBlobStorage* aBlobStorage, nsresult aRv)
+      : Runnable("dom::ErrorPropagationRunnable"),
+        mBlobStorage(aBlobStorage),
+        mRv(aRv) {}
+
+  NS_IMETHOD
+  Run() override {
+    mBlobStorage->ErrorPropagated(mRv);
+    return NS_OK;
+  }
+
+ private:
+  RefPtr<MutableBlobStorage> mBlobStorage;
+  nsresult mRv;
+};
+
+// This runnable moves a buffer to the IO thread and there, it writes it into
+// the temporary file, if its File Descriptor has not been already closed.
+class WriteRunnable final : public Runnable {
+ public:
+  static WriteRunnable* CopyBuffer(MutableBlobStorage* aBlobStorage,
+                                   const void* aData, uint32_t aLength) {
+    MOZ_ASSERT(aBlobStorage);
+    MOZ_ASSERT(aData);
+
+    // We have to take a copy of this buffer.
+    void* data = malloc(aLength);
+    if (!data) {
+      return nullptr;
+    }
+
+    memcpy((char*)data, aData, aLength);
+    return new WriteRunnable(aBlobStorage, data, aLength);
+  }
+
+  static WriteRunnable* AdoptBuffer(MutableBlobStorage* aBlobStorage,
+                                    void* aData, uint32_t aLength) {
+    MOZ_ASSERT(NS_IsMainThread());
+    MOZ_ASSERT(aBlobStorage);
+    MOZ_ASSERT(aData);
+
+    return new WriteRunnable(aBlobStorage, aData, aLength);
+  }
+
+  NS_IMETHOD
+  Run() override {
+    MOZ_ASSERT(!NS_IsMainThread());
+    MOZ_ASSERT(mBlobStorage);
+
+    PRFileDesc* fd = mBlobStorage->GetFD();
+    if (!fd) {
+      // The file descriptor has been closed in the meantime.
+      return NS_OK;
+    }
+
+    int32_t written = PR_Write(fd, mData, mLength);
+    if (NS_WARN_IF(written < 0 || uint32_t(written) != mLength)) {
+      mBlobStorage->CloseFD();
+      return mBlobStorage->EventTarget()->Dispatch(
+          new ErrorPropagationRunnable(mBlobStorage, NS_ERROR_FAILURE),
+          NS_DISPATCH_NORMAL);
+    }
+
+    return NS_OK;
+  }
+
+ private:
+  WriteRunnable(MutableBlobStorage* aBlobStorage, void* aData, uint32_t aLength)
+      : Runnable("dom::WriteRunnable"),
+        mBlobStorage(aBlobStorage),
+        mData(aData),
+        mLength(aLength) {
+    MOZ_ASSERT(mBlobStorage);
+    MOZ_ASSERT(aData);
+  }
+
+  ~WriteRunnable() override { free(mData); }
+
+  RefPtr<MutableBlobStorage> mBlobStorage;
+  void* mData;
+  uint32_t mLength;
+};
+
+// This runnable closes the FD in case something goes wrong or the temporary
+// file is not needed anymore.
+class CloseFileRunnable final : public Runnable {
+ public:
+  explicit CloseFileRunnable(PRFileDesc* aFD)
+      : Runnable("dom::CloseFileRunnable"), mFD(aFD) {}
+
+  NS_IMETHOD
+  Run() override {
+    MOZ_ASSERT(!NS_IsMainThread());
+    PR_Close(mFD);
+    mFD = nullptr;
+    return NS_OK;
+  }
+
+ private:
+  ~CloseFileRunnable() override {
+    if (mFD) {
+      PR_Close(mFD);
+    }
+  }
+
+  PRFileDesc* mFD;
+};
+
+// This runnable is dispatched to the main-thread from the IO thread and its
+// task is to create the blob and inform the callback.
+class CreateBlobRunnable final : public Runnable,
+                                 public TemporaryIPCBlobChildCallback {
+ public:
+  // We need to always declare refcounting because
+  // TemporaryIPCBlobChildCallback has pure-virtual refcounting.
+  NS_DECL_ISUPPORTS_INHERITED
+
+  CreateBlobRunnable(MutableBlobStorage* aBlobStorage,
+                     const nsACString& aContentType,
+                     already_AddRefed<MutableBlobStorageCallback> aCallback)
+      : Runnable("dom::CreateBlobRunnable"),
+        mBlobStorage(aBlobStorage),
+        mContentType(aContentType),
+        mCallback(aCallback) {
+    MOZ_ASSERT(!NS_IsMainThread());
+    MOZ_ASSERT(aBlobStorage);
+  }
+
+  NS_IMETHOD
+  Run() override {
+    MOZ_ASSERT(NS_IsMainThread());
+    MOZ_ASSERT(mBlobStorage);
+    mBlobStorage->AskForBlob(this, mContentType);
+    return NS_OK;
+  }
+
+  void OperationSucceeded(BlobImpl* aBlobImpl) override {
+    RefPtr<MutableBlobStorageCallback> callback(std::move(mCallback));
+    callback->BlobStoreCompleted(mBlobStorage, aBlobImpl, NS_OK);
+  }
+
+  void OperationFailed(nsresult aRv) override {
+    RefPtr<MutableBlobStorageCallback> callback(std::move(mCallback));
+    callback->BlobStoreCompleted(mBlobStorage, nullptr, aRv);
+  }
+
+ private:
+  ~CreateBlobRunnable() override {
+    MOZ_ASSERT(mBlobStorage);
+    // If something when wrong, we still have to release data in the correct
+    // thread.
+    NS_ProxyRelease("CreateBlobRunnable::mCallback",
+                    mBlobStorage->EventTarget(), mCallback.forget());
+  }
+
+  RefPtr<MutableBlobStorage> mBlobStorage;
+  nsCString mContentType;
+  RefPtr<MutableBlobStorageCallback> mCallback;
+};
+
+NS_IMPL_ISUPPORTS_INHERITED0(CreateBlobRunnable, Runnable)
+
+// This task is used to know when the writing is completed. From the IO thread
+// it dispatches a CreateBlobRunnable to the main-thread.
+class LastRunnable final : public Runnable {
+ public:
+  LastRunnable(MutableBlobStorage* aBlobStorage, const nsACString& aContentType,
+               MutableBlobStorageCallback* aCallback)
+      : Runnable("dom::LastRunnable"),
+        mBlobStorage(aBlobStorage),
+        mContentType(aContentType),
+        mCallback(aCallback) {
+    MOZ_ASSERT(NS_IsMainThread());
+    MOZ_ASSERT(mBlobStorage);
+    MOZ_ASSERT(aCallback);
+  }
+
+  NS_IMETHOD
+  Run() override {
+    MOZ_ASSERT(!NS_IsMainThread());
+
+    RefPtr<Runnable> runnable =
+        new CreateBlobRunnable(mBlobStorage, mContentType, mCallback.forget());
+    return mBlobStorage->EventTarget()->Dispatch(runnable, NS_DISPATCH_NORMAL);
+  }
+
+ private:
+  ~LastRunnable() override {
+    MOZ_ASSERT(mBlobStorage);
+    // If something when wrong, we still have to release data in the correct
+    // thread.
+    NS_ProxyRelease("LastRunnable::mCallback", mBlobStorage->EventTarget(),
+                    mCallback.forget());
+  }
+
+  RefPtr<MutableBlobStorage> mBlobStorage;
+  nsCString mContentType;
+  RefPtr<MutableBlobStorageCallback> mCallback;
+};
+
+}  // anonymous namespace
+
+MutableBlobStorage::MutableBlobStorage(MutableBlobStorageType aType,
+                                       nsIEventTarget* aEventTarget,
+                                       uint32_t aMaxMemory)
+    : mMutex("MutableBlobStorage::mMutex"),
+      mData(nullptr),
+      mDataLen(0),
+      mDataBufferLen(0),
+      mStorageState(aType == eOnlyInMemory ? eKeepInMemory : eInMemory),
+      mFD(nullptr),
+      mErrorResult(NS_OK),
+      mEventTarget(aEventTarget),
+      mMaxMemory(aMaxMemory) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!mEventTarget) {
+    mEventTarget = GetMainThreadEventTarget();
+  }
+
+  if (aMaxMemory == 0 && aType == eCouldBeInTemporaryFile) {
+    mMaxMemory = Preferences::GetUint("dom.blob.memoryToTemporaryFile",
+                                      BLOB_MEMORY_TEMPORARY_FILE);
+  }
+
+  MOZ_ASSERT(mEventTarget);
+}
+
+MutableBlobStorage::~MutableBlobStorage() {
+  free(mData);
+
+  if (mFD) {
+    RefPtr<Runnable> runnable = new CloseFileRunnable(mFD);
+    Unused << DispatchToIOThread(runnable.forget());
+  }
+
+  if (mTaskQueue) {
+    mTaskQueue->BeginShutdown();
+  }
+
+  if (mActor) {
+    NS_ProxyRelease("MutableBlobStorage::mActor", EventTarget(),
+                    mActor.forget());
+  }
+}
+
+void MutableBlobStorage::GetBlobImplWhenReady(
+    const nsACString& aContentType, MutableBlobStorageCallback* aCallback) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(aCallback);
+
+  MutexAutoLock lock(mMutex);
+
+  // GetBlob can be called just once.
+  MOZ_ASSERT(mStorageState != eClosed);
+  StorageState previousState = mStorageState;
+  mStorageState = eClosed;
+
+  if (previousState == eInTemporaryFile) {
+    if (NS_FAILED(mErrorResult)) {
+      MOZ_ASSERT(!mActor);
+
+      RefPtr<Runnable> runnable =
+          new BlobCreationDoneRunnable(this, aCallback, nullptr, mErrorResult);
+      EventTarget()->Dispatch(runnable.forget(), NS_DISPATCH_NORMAL);
+      return;
+    }
+
+    MOZ_ASSERT(mActor);
+
+    // We want to wait until all the WriteRunnable are completed. The way we do
+    // this is to go to the I/O thread and then we come back: the runnables are
+    // executed in order and this LastRunnable will be... the last one.
+    // This Runnable will also close the FD on the I/O thread.
+    RefPtr<Runnable> runnable = new LastRunnable(this, aContentType, aCallback);
+
+    // If the dispatching fails, we are shutting down and it's fine to do not
+    // run the callback.
+    Unused << DispatchToIOThread(runnable.forget());
+    return;
+  }
+
+  // If we are waiting for the temporary file, it's better to wait...
+  if (previousState == eWaitingForTemporaryFile) {
+    mPendingContentType = aContentType;
+    mPendingCallback = aCallback;
+    return;
+  }
+
+  RefPtr<BlobImpl> blobImpl;
+
+  if (mData) {
+    blobImpl = new MemoryBlobImpl(mData, mDataLen,
+                                  NS_ConvertUTF8toUTF16(aContentType));
+
+    mData = nullptr;  // The MemoryBlobImpl takes ownership of the buffer
+    mDataLen = 0;
+    mDataBufferLen = 0;
+  } else {
+    blobImpl = new EmptyBlobImpl(NS_ConvertUTF8toUTF16(aContentType));
+  }
+
+  RefPtr<BlobCreationDoneRunnable> runnable =
+      new BlobCreationDoneRunnable(this, aCallback, blobImpl, NS_OK);
+
+  nsresult error =
+      EventTarget()->Dispatch(runnable.forget(), NS_DISPATCH_NORMAL);
+  if (NS_WARN_IF(NS_FAILED(error))) {
+    return;
+  }
+}
+
+nsresult MutableBlobStorage::Append(const void* aData, uint32_t aLength) {
+  // This method can be called on any thread.
+
+  MutexAutoLock lock(mMutex);
+  MOZ_ASSERT(mStorageState != eClosed);
+  NS_ENSURE_ARG_POINTER(aData);
+
+  if (!aLength) {
+    return NS_OK;
+  }
+
+  // If eInMemory is the current Storage state, we could maybe migrate to
+  // a temporary file.
+  if (mStorageState == eInMemory && ShouldBeTemporaryStorage(lock, aLength) &&
+      !MaybeCreateTemporaryFile(lock)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // If we are already in the temporaryFile mode, we have to dispatch a
+  // runnable.
+  if (mStorageState == eInTemporaryFile) {
+    // If a previous operation failed, let's return that error now.
+    if (NS_FAILED(mErrorResult)) {
+      return mErrorResult;
+    }
+
+    RefPtr<WriteRunnable> runnable =
+        WriteRunnable::CopyBuffer(this, aData, aLength);
+    if (NS_WARN_IF(!runnable)) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+
+    nsresult rv = DispatchToIOThread(runnable.forget());
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    mDataLen += aLength;
+    return NS_OK;
+  }
+
+  // By default, we store in memory.
+
+  uint64_t offset = mDataLen;
+
+  if (!ExpandBufferSize(lock, aLength)) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  memcpy((char*)mData + offset, aData, aLength);
+  return NS_OK;
+}
+
+bool MutableBlobStorage::ExpandBufferSize(const MutexAutoLock& aProofOfLock,
+                                          uint64_t aSize) {
+  MOZ_ASSERT(mStorageState < eInTemporaryFile);
+
+  if (mDataBufferLen >= mDataLen + aSize) {
+    mDataLen += aSize;
+    return true;
+  }
+
+  // Start at 1 or we'll loop forever.
+  CheckedUint32 bufferLen =
+      std::max<uint32_t>(static_cast<uint32_t>(mDataBufferLen), 1);
+  while (bufferLen.isValid() && bufferLen.value() < mDataLen + aSize) {
+    bufferLen *= 2;
+  }
+
+  if (!bufferLen.isValid()) {
+    return false;
+  }
+
+  void* data = realloc(mData, bufferLen.value());
+  if (!data) {
+    return false;
+  }
+
+  mData = data;
+  mDataBufferLen = bufferLen.value();
+  mDataLen += aSize;
+  return true;
+}
+
+bool MutableBlobStorage::ShouldBeTemporaryStorage(
+    const MutexAutoLock& aProofOfLock, uint64_t aSize) const {
+  MOZ_ASSERT(mStorageState == eInMemory);
+
+  CheckedUint32 bufferSize = mDataLen;
+  bufferSize += aSize;
+
+  if (!bufferSize.isValid()) {
+    return false;
+  }
+
+  return bufferSize.value() >= mMaxMemory;
+}
+
+bool MutableBlobStorage::MaybeCreateTemporaryFile(
+    const MutexAutoLock& aProofOfLock) {
+  mStorageState = eWaitingForTemporaryFile;
+
+  if (!NS_IsMainThread()) {
+    RefPtr<MutableBlobStorage> self = this;
+    nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction(
+        "MutableBlobStorage::MaybeCreateTemporaryFile", [self]() {
+          MutexAutoLock lock(self->mMutex);
+          self->MaybeCreateTemporaryFileOnMainThread(lock);
+          if (!self->mActor) {
+            self->ErrorPropagated(NS_ERROR_FAILURE);
+          }
+        });
+    EventTarget()->Dispatch(r.forget(), NS_DISPATCH_NORMAL);
+    return true;
+  }
+
+  MaybeCreateTemporaryFileOnMainThread(aProofOfLock);
+  return !!mActor;
+}
+
+void MutableBlobStorage::MaybeCreateTemporaryFileOnMainThread(
+    const MutexAutoLock& aProofOfLock) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(!mActor);
+
+  mozilla::ipc::PBackgroundChild* actorChild =
+      mozilla::ipc::BackgroundChild::GetOrCreateForCurrentThread();
+  if (NS_WARN_IF(!actorChild)) {
+    return;
+  }
+
+  mActor = new TemporaryIPCBlobChild(this);
+  actorChild->SendPTemporaryIPCBlobConstructor(mActor);
+
+  // We need manually to increase the reference for this actor because the
+  // IPC allocator method is not triggered. The Release() is called by IPDL
+  // when the actor is deleted.
+  mActor.get()->AddRef();
+
+  // The actor will call us when the FileDescriptor is received.
+}
+
+void MutableBlobStorage::TemporaryFileCreated(PRFileDesc* aFD) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  MutexAutoLock lock(mMutex);
+  MOZ_ASSERT(mStorageState == eWaitingForTemporaryFile ||
+             mStorageState == eClosed);
+  MOZ_ASSERT_IF(mPendingCallback, mStorageState == eClosed);
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(aFD);
+
+  // If the object has been already closed and we don't need to execute a
+  // callback, we need just to close the file descriptor in the correct thread.
+  if (mStorageState == eClosed && !mPendingCallback) {
+    RefPtr<Runnable> runnable = new CloseFileRunnable(aFD);
+
+    // If this dispatching fails, CloseFileRunnable will close the FD in the
+    // DTOR on the current thread.
+    Unused << DispatchToIOThread(runnable.forget());
+
+    // Let's inform the parent that we have nothing else to do.
+    mActor->SendOperationFailed();
+    mActor = nullptr;
+    return;
+  }
+
+  // If we still receiving data, we can proceed in temporary-file mode.
+  if (mStorageState == eWaitingForTemporaryFile) {
+    mStorageState = eInTemporaryFile;
+  }
+
+  mFD = aFD;
+  MOZ_ASSERT(NS_SUCCEEDED(mErrorResult));
+
+  // This runnable takes the ownership of mData and it will write this buffer
+  // into the temporary file.
+  RefPtr<WriteRunnable> runnable =
+      WriteRunnable::AdoptBuffer(this, mData, mDataLen);
+  MOZ_ASSERT(runnable);
+
+  mData = nullptr;
+
+  nsresult rv = DispatchToIOThread(runnable.forget());
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    // Shutting down, we cannot continue.
+    return;
+  }
+
+  // If we are closed, it means that GetBlobImplWhenReady() has been called when
+  // we were already waiting for a temporary file-descriptor. Finally we are
+  // here, AdoptBuffer runnable is going to write the current buffer into this
+  // file. After that, there is nothing else to write, and we dispatch
+  // LastRunnable which ends up calling mPendingCallback via CreateBlobRunnable.
+  if (mStorageState == eClosed) {
+    MOZ_ASSERT(mPendingCallback);
+
+    RefPtr<Runnable> runnable =
+        new LastRunnable(this, mPendingContentType, mPendingCallback);
+    Unused << DispatchToIOThread(runnable.forget());
+
+    mPendingCallback = nullptr;
+  }
+}
+
+void MutableBlobStorage::AskForBlob(TemporaryIPCBlobChildCallback* aCallback,
+                                    const nsACString& aContentType) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  MutexAutoLock lock(mMutex);
+  MOZ_ASSERT(mStorageState == eClosed);
+  MOZ_ASSERT(mFD);
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(aCallback);
+
+  // Let's pass the FileDescriptor to the parent actor in order to keep the file
+  // locked on windows.
+  mActor->AskForBlob(aCallback, aContentType, mFD);
+
+  // The previous operation has duplicated the file descriptor. Now we can close
+  // mFD. The parent will take care of closing the duplicated file descriptor on
+  // its side.
+  RefPtr<Runnable> runnable = new CloseFileRunnable(mFD);
+  Unused << DispatchToIOThread(runnable.forget());
+
+  mFD = nullptr;
+  mActor = nullptr;
+}
+
+void MutableBlobStorage::ErrorPropagated(nsresult aRv) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  MutexAutoLock lock(mMutex);
+  mErrorResult = aRv;
+
+  if (mActor) {
+    mActor->SendOperationFailed();
+    mActor = nullptr;
+  }
+}
+
+nsresult MutableBlobStorage::DispatchToIOThread(
+    already_AddRefed<nsIRunnable> aRunnable) {
+  if (!mTaskQueue) {
+    nsCOMPtr<nsIEventTarget> target =
+        do_GetService(NS_STREAMTRANSPORTSERVICE_CONTRACTID);
+    MOZ_ASSERT(target);
+
+    mTaskQueue = TaskQueue::Create(target.forget(), "BlobStorage");
+  }
+
+  nsCOMPtr<nsIRunnable> runnable(aRunnable);
+  nsresult rv = mTaskQueue->Dispatch(runnable.forget());
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+size_t MutableBlobStorage::SizeOfCurrentMemoryBuffer() {
+  MOZ_ASSERT(NS_IsMainThread());
+  MutexAutoLock lock(mMutex);
+  return mStorageState < eInTemporaryFile ? mDataLen : 0;
+}
+
+PRFileDesc* MutableBlobStorage::GetFD() {
+  MOZ_ASSERT(!NS_IsMainThread());
+  MutexAutoLock lock(mMutex);
+  return mFD;
+}
+
+void MutableBlobStorage::CloseFD() {
+  MOZ_ASSERT(!NS_IsMainThread());
+  MutexAutoLock lock(mMutex);
+  MOZ_ASSERT(mFD);
+
+  PR_Close(mFD);
+  mFD = nullptr;
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/MutableBlobStorage.h b/dom/file/MutableBlobStorage.h
new file mode 100644
index 0000000000..aa0d42c75e
--- /dev/null
+++ b/dom/file/MutableBlobStorage.h
@@ -0,0 +1,136 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_MutableBlobStorage_h
+#define mozilla_dom_MutableBlobStorage_h
+
+#include "mozilla/RefPtr.h"
+#include "mozilla/Mutex.h"
+#include "nsCOMPtr.h"
+#include "nsString.h"
+#include "prio.h"
+
+class nsIEventTarget;
+class nsIRunnable;
+
+namespace mozilla {
+
+class TaskQueue;
+
+namespace dom {
+
+class Blob;
+class BlobImpl;
+class MutableBlobStorage;
+class TemporaryIPCBlobChild;
+class TemporaryIPCBlobChildCallback;
+
+class MutableBlobStorageCallback {
+ public:
+  NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
+
+  virtual void BlobStoreCompleted(MutableBlobStorage* aBlobStorage,
+                                  BlobImpl* aBlob, nsresult aRv) = 0;
+};
+
+// This class is must be created and used on main-thread, except for Append()
+// that can be called on any thread.
+class MutableBlobStorage final {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(MutableBlobStorage)
+
+  enum MutableBlobStorageType {
+    eOnlyInMemory,
+    eCouldBeInTemporaryFile,
+  };
+
+  explicit MutableBlobStorage(MutableBlobStorageType aType,
+                              nsIEventTarget* aEventTarget = nullptr,
+                              uint32_t aMaxMemory = 0);
+
+  nsresult Append(const void* aData, uint32_t aLength);
+
+  // This method can be called just once.
+  // The callback will be called when the BlobImpl is ready.
+  void GetBlobImplWhenReady(const nsACString& aContentType,
+                            MutableBlobStorageCallback* aCallback);
+
+  void TemporaryFileCreated(PRFileDesc* aFD);
+
+  void AskForBlob(TemporaryIPCBlobChildCallback* aCallback,
+                  const nsACString& aContentType);
+
+  void ErrorPropagated(nsresult aRv);
+
+  nsIEventTarget* EventTarget() {
+    MOZ_ASSERT(mEventTarget);
+    return mEventTarget;
+  }
+
+  // Returns the heap size in bytes of our internal buffers.
+  // Note that this intentionally ignores the data in the temp file.
+  size_t SizeOfCurrentMemoryBuffer();
+
+  PRFileDesc* GetFD();
+
+  void CloseFD();
+
+ private:
+  ~MutableBlobStorage();
+
+  bool ExpandBufferSize(const MutexAutoLock& aProofOfLock, uint64_t aSize);
+
+  bool ShouldBeTemporaryStorage(const MutexAutoLock& aProofOfLock,
+                                uint64_t aSize) const;
+
+  bool MaybeCreateTemporaryFile(const MutexAutoLock& aProofOfLock);
+  void MaybeCreateTemporaryFileOnMainThread(const MutexAutoLock& aProofOfLock);
+
+  [[nodiscard]] nsresult DispatchToIOThread(
+      already_AddRefed<nsIRunnable> aRunnable);
+
+  Mutex mMutex MOZ_UNANNOTATED;
+
+  // All these variables are touched on the main thread only or in the
+  // retargeted thread when used by Append(). They are protected by mMutex.
+
+  void* mData;
+  uint64_t mDataLen;
+  uint64_t mDataBufferLen;
+
+  enum StorageState {
+    eKeepInMemory,
+    eInMemory,
+    eWaitingForTemporaryFile,
+    eInTemporaryFile,
+    eClosed
+  };
+
+  StorageState mStorageState;
+
+  PRFileDesc* mFD;
+
+  nsresult mErrorResult;
+
+  RefPtr<TaskQueue> mTaskQueue;
+  nsCOMPtr<nsIEventTarget> mEventTarget;
+
+  nsCString mPendingContentType;
+  RefPtr<MutableBlobStorageCallback> mPendingCallback;
+
+  RefPtr<TemporaryIPCBlobChild> mActor;
+
+  // This value is used when we go from eInMemory to eWaitingForTemporaryFile
+  // and eventually eInTemporaryFile. If the size of the buffer is >=
+  // mMaxMemory, the creation of the temporary file will start.
+  // It's not used if mStorageState is eKeepInMemory.
+  uint32_t mMaxMemory;
+};
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // mozilla_dom_MutableBlobStorage_h
diff --git a/dom/file/MutableBlobStreamListener.cpp b/dom/file/MutableBlobStreamListener.cpp
new file mode 100644
index 0000000000..f5031267cc
--- /dev/null
+++ b/dom/file/MutableBlobStreamListener.cpp
@@ -0,0 +1,102 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "MutableBlobStreamListener.h"
+#include "MutableBlobStorage.h"
+#include "nsIInputStream.h"
+#include "nsThreadUtils.h"
+
+namespace mozilla::dom {
+
+MutableBlobStreamListener::MutableBlobStreamListener(
+    MutableBlobStorage::MutableBlobStorageType aStorageType,
+    const nsACString& aContentType, MutableBlobStorageCallback* aCallback,
+    nsIEventTarget* aEventTarget)
+    : mCallback(aCallback),
+      mStorageType(aStorageType),
+      mContentType(aContentType),
+      mEventTarget(aEventTarget) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(aCallback);
+
+  if (!mEventTarget) {
+    mEventTarget = GetMainThreadEventTarget();
+  }
+
+  MOZ_ASSERT(mEventTarget);
+}
+
+MutableBlobStreamListener::~MutableBlobStreamListener() {
+  MOZ_ASSERT(NS_IsMainThread());
+}
+
+NS_IMPL_ISUPPORTS(MutableBlobStreamListener, nsIStreamListener,
+                  nsIThreadRetargetableStreamListener, nsIRequestObserver)
+
+NS_IMETHODIMP
+MutableBlobStreamListener::OnStartRequest(nsIRequest* aRequest) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(!mStorage);
+  MOZ_ASSERT(mEventTarget);
+
+  mStorage = new MutableBlobStorage(mStorageType, mEventTarget);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+MutableBlobStreamListener::OnStopRequest(nsIRequest* aRequest,
+                                         nsresult aStatus) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(mStorage);
+
+  // Resetting mStorage to nullptr.
+  RefPtr<MutableBlobStorage> storage;
+  storage.swap(mStorage);
+
+  // Let's propagate the error simulating a failure of the storage.
+  if (NS_FAILED(aStatus)) {
+    mCallback->BlobStoreCompleted(storage, nullptr, aStatus);
+    return NS_OK;
+  }
+
+  storage->GetBlobImplWhenReady(mContentType, mCallback);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+MutableBlobStreamListener::OnDataAvailable(nsIRequest* aRequest,
+                                           nsIInputStream* aStream,
+                                           uint64_t aSourceOffset,
+                                           uint32_t aCount) {
+  // This method could be called on any thread.
+  MOZ_ASSERT(mStorage);
+
+  uint32_t countRead;
+  return aStream->ReadSegments(WriteSegmentFun, this, aCount, &countRead);
+}
+
+nsresult MutableBlobStreamListener::WriteSegmentFun(
+    nsIInputStream* aWriterStream, void* aClosure, const char* aFromSegment,
+    uint32_t aToOffset, uint32_t aCount, uint32_t* aWriteCount) {
+  // This method could be called on any thread.
+
+  MutableBlobStreamListener* self =
+      static_cast<MutableBlobStreamListener*>(aClosure);
+  MOZ_ASSERT(self->mStorage);
+
+  nsresult rv = self->mStorage->Append(aFromSegment, aCount);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  *aWriteCount = aCount;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+MutableBlobStreamListener::CheckListenerChain() { return NS_OK; }
+
+}  // namespace mozilla::dom
diff --git a/dom/file/MutableBlobStreamListener.h b/dom/file/MutableBlobStreamListener.h
new file mode 100644
index 0000000000..6fd32848a7
--- /dev/null
+++ b/dom/file/MutableBlobStreamListener.h
@@ -0,0 +1,50 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_MutableBlobStreamListener_h
+#define mozilla_dom_MutableBlobStreamListener_h
+
+#include "nsIStreamListener.h"
+#include "nsIThreadRetargetableStreamListener.h"
+#include "nsTString.h"
+#include "mozilla/dom/MutableBlobStorage.h"
+
+class nsIEventTarget;
+
+namespace mozilla::dom {
+
+class MutableBlobStreamListener final
+    : public nsIStreamListener,
+      public nsIThreadRetargetableStreamListener {
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSISTREAMLISTENER
+  NS_DECL_NSITHREADRETARGETABLESTREAMLISTENER
+  NS_DECL_NSIREQUESTOBSERVER
+
+  MutableBlobStreamListener(
+      MutableBlobStorage::MutableBlobStorageType aStorageType,
+      const nsACString& aContentType, MutableBlobStorageCallback* aCallback,
+      nsIEventTarget* aEventTarget = nullptr);
+
+ private:
+  ~MutableBlobStreamListener();
+
+  static nsresult WriteSegmentFun(nsIInputStream* aWriter, void* aClosure,
+                                  const char* aFromSegment, uint32_t aOffset,
+                                  uint32_t aCount, uint32_t* aWriteCount);
+
+  RefPtr<MutableBlobStorage> mStorage;
+  RefPtr<MutableBlobStorageCallback> mCallback;
+
+  MutableBlobStorage::MutableBlobStorageType mStorageType;
+  nsCString mContentType;
+  nsCOMPtr<nsIEventTarget> mEventTarget;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_MutableBlobStreamListener_h
diff --git a/dom/file/StreamBlobImpl.cpp b/dom/file/StreamBlobImpl.cpp
new file mode 100644
index 0000000000..9d0c8d86d1
--- /dev/null
+++ b/dom/file/StreamBlobImpl.cpp
@@ -0,0 +1,224 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "EmptyBlobImpl.h"
+#include "mozilla/InputStreamLengthWrapper.h"
+#include "mozilla/SlicedInputStream.h"
+#include "StreamBlobImpl.h"
+#include "nsNetCID.h"
+#include "nsServiceManagerUtils.h"
+#include "nsStreamUtils.h"
+#include "nsStringStream.h"
+#include "nsIAsyncOutputStream.h"
+#include "nsICloneableInputStream.h"
+#include "nsIEventTarget.h"
+#include "nsIPipe.h"
+
+namespace mozilla::dom {
+
+NS_IMPL_ISUPPORTS_INHERITED(StreamBlobImpl, BlobImpl, nsIMemoryReporter)
+
+static already_AddRefed<nsICloneableInputStream> EnsureCloneableStream(
+    nsIInputStream* aInputStream, uint64_t aLength) {
+  nsCOMPtr<nsICloneableInputStream> cloneable = do_QueryInterface(aInputStream);
+  if (cloneable && cloneable->GetCloneable()) {
+    return cloneable.forget();
+  }
+
+  // If the stream we're copying is known to be small, specify the size of the
+  // pipe's segments precisely to limit wasted space. An extra byte above length
+  // is included to avoid allocating an extra segment immediately before reading
+  // EOF from the source stream.  Otherwise, allocate 64k buffers rather than
+  // the default of 4k buffers to reduce segment counts for very large payloads.
+  static constexpr uint32_t kBaseSegmentSize = 64 * 1024;
+  uint32_t segmentSize = kBaseSegmentSize;
+  if (aLength + 1 <= kBaseSegmentSize * 4) {
+    segmentSize = aLength + 1;
+  }
+
+  // NOTE: We specify unlimited segments to eagerly build a complete copy of the
+  // source stream locally without waiting for the blob to be consumed.
+  nsCOMPtr<nsIAsyncInputStream> reader;
+  nsCOMPtr<nsIAsyncOutputStream> writer;
+  NS_NewPipe2(getter_AddRefs(reader), getter_AddRefs(writer), true, true,
+              segmentSize, UINT32_MAX);
+
+  nsresult rv;
+  nsCOMPtr<nsIEventTarget> target =
+      do_GetService(NS_STREAMTRANSPORTSERVICE_CONTRACTID, &rv);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+
+  rv = NS_AsyncCopy(aInputStream, writer, target,
+                    NS_ASYNCCOPY_VIA_WRITESEGMENTS, segmentSize);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+
+  cloneable = do_QueryInterface(reader);
+  MOZ_ASSERT(cloneable && cloneable->GetCloneable());
+  return cloneable.forget();
+}
+
+/* static */
+already_AddRefed<StreamBlobImpl> StreamBlobImpl::Create(
+    already_AddRefed<nsIInputStream> aInputStream,
+    const nsAString& aContentType, uint64_t aLength,
+    const nsAString& aBlobImplType) {
+  nsCOMPtr<nsIInputStream> inputStream = std::move(aInputStream);
+  nsCOMPtr<nsICloneableInputStream> cloneable =
+      EnsureCloneableStream(inputStream, aLength);
+
+  RefPtr<StreamBlobImpl> blobImplStream = new StreamBlobImpl(
+      cloneable.forget(), aContentType, aLength, aBlobImplType);
+  blobImplStream->MaybeRegisterMemoryReporter();
+  return blobImplStream.forget();
+}
+
+/* static */
+already_AddRefed<StreamBlobImpl> StreamBlobImpl::Create(
+    already_AddRefed<nsIInputStream> aInputStream, const nsAString& aName,
+    const nsAString& aContentType, int64_t aLastModifiedDate, uint64_t aLength,
+    const nsAString& aBlobImplType) {
+  nsCOMPtr<nsIInputStream> inputStream = std::move(aInputStream);
+  nsCOMPtr<nsICloneableInputStream> cloneable =
+      EnsureCloneableStream(inputStream, aLength);
+
+  RefPtr<StreamBlobImpl> blobImplStream =
+      new StreamBlobImpl(cloneable.forget(), aName, aContentType,
+                         aLastModifiedDate, aLength, aBlobImplType);
+  blobImplStream->MaybeRegisterMemoryReporter();
+  return blobImplStream.forget();
+}
+
+StreamBlobImpl::StreamBlobImpl(
+    already_AddRefed<nsICloneableInputStream> aInputStream,
+    const nsAString& aContentType, uint64_t aLength,
+    const nsAString& aBlobImplType)
+    : BaseBlobImpl(aContentType, aLength),
+      mInputStream(std::move(aInputStream)),
+      mBlobImplType(aBlobImplType),
+      mIsDirectory(false),
+      mFileId(-1) {}
+
+StreamBlobImpl::StreamBlobImpl(
+    already_AddRefed<nsICloneableInputStream> aInputStream,
+    const nsAString& aName, const nsAString& aContentType,
+    int64_t aLastModifiedDate, uint64_t aLength, const nsAString& aBlobImplType)
+    : BaseBlobImpl(aName, aContentType, aLength, aLastModifiedDate),
+      mInputStream(std::move(aInputStream)),
+      mBlobImplType(aBlobImplType),
+      mIsDirectory(false),
+      mFileId(-1) {}
+
+StreamBlobImpl::~StreamBlobImpl() {
+  if (mInputStream) {
+    nsCOMPtr<nsIInputStream> stream = do_QueryInterface(mInputStream);
+    stream->Close();
+  }
+  UnregisterWeakMemoryReporter(this);
+}
+
+void StreamBlobImpl::CreateInputStream(nsIInputStream** aStream,
+                                       ErrorResult& aRv) const {
+  if (!mInputStream) {
+    // We failed to clone the input stream in EnsureCloneableStream.
+    *aStream = nullptr;
+    aRv.ThrowUnknownError("failed to read blob data");
+    return;
+  }
+
+  nsCOMPtr<nsIInputStream> clonedStream;
+  aRv = mInputStream->Clone(getter_AddRefs(clonedStream));
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  nsCOMPtr<nsIInputStream> wrappedStream =
+      InputStreamLengthWrapper::MaybeWrap(clonedStream.forget(), mLength);
+
+  wrappedStream.forget(aStream);
+}
+
+already_AddRefed<BlobImpl> StreamBlobImpl::CreateSlice(
+    uint64_t aStart, uint64_t aLength, const nsAString& aContentType,
+    ErrorResult& aRv) const {
+  if (!aLength) {
+    RefPtr<BlobImpl> impl = new EmptyBlobImpl(aContentType);
+    return impl.forget();
+  }
+
+  nsCOMPtr<nsIInputStream> clonedStream;
+
+  nsCOMPtr<nsICloneableInputStreamWithRange> stream =
+      do_QueryInterface(mInputStream);
+  if (stream) {
+    aRv = stream->CloneWithRange(aStart, aLength, getter_AddRefs(clonedStream));
+    if (NS_WARN_IF(aRv.Failed())) {
+      return nullptr;
+    }
+  } else {
+    CreateInputStream(getter_AddRefs(clonedStream), aRv);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return nullptr;
+    }
+
+    clonedStream =
+        new SlicedInputStream(clonedStream.forget(), aStart, aLength);
+  }
+
+  MOZ_ASSERT(clonedStream);
+
+  return StreamBlobImpl::Create(clonedStream.forget(), aContentType, aLength,
+                                mBlobImplType);
+}
+
+void StreamBlobImpl::MaybeRegisterMemoryReporter() {
+  // We report only stringInputStream.
+  nsCOMPtr<nsIStringInputStream> stringInputStream =
+      do_QueryInterface(mInputStream);
+  if (!stringInputStream) {
+    return;
+  }
+
+  RegisterWeakMemoryReporter(this);
+}
+
+NS_IMETHODIMP
+StreamBlobImpl::CollectReports(nsIHandleReportCallback* aHandleReport,
+                               nsISupports* aData, bool aAnonymize) {
+  nsCOMPtr<nsIStringInputStream> stringInputStream =
+      do_QueryInterface(mInputStream);
+  if (!stringInputStream) {
+    return NS_OK;
+  }
+
+  MOZ_COLLECT_REPORT(
+      "explicit/dom/memory-file-data/stream", KIND_HEAP, UNITS_BYTES,
+      stringInputStream->SizeOfIncludingThisIfUnshared(MallocSizeOf),
+      "Memory used to back a File/Blob based on an input stream.");
+
+  return NS_OK;
+}
+
+size_t StreamBlobImpl::GetAllocationSize() const {
+  nsCOMPtr<nsIStringInputStream> stringInputStream =
+      do_QueryInterface(mInputStream);
+  if (!stringInputStream) {
+    return 0;
+  }
+
+  return stringInputStream->SizeOfIncludingThisEvenIfShared(MallocSizeOf);
+}
+
+void StreamBlobImpl::GetBlobImplType(nsAString& aBlobImplType) const {
+  aBlobImplType.AssignLiteral("StreamBlobImpl[");
+  aBlobImplType.Append(mBlobImplType);
+  aBlobImplType.AppendLiteral("]");
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/StreamBlobImpl.h b/dom/file/StreamBlobImpl.h
new file mode 100644
index 0000000000..6f35638463
--- /dev/null
+++ b/dom/file/StreamBlobImpl.h
@@ -0,0 +1,95 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_StreamBlobImpl_h
+#define mozilla_dom_StreamBlobImpl_h
+
+#include "BaseBlobImpl.h"
+#include "nsCOMPtr.h"
+#include "nsIMemoryReporter.h"
+#include "nsICloneableInputStream.h"
+
+namespace mozilla::dom {
+
+class StreamBlobImpl final : public BaseBlobImpl, public nsIMemoryReporter {
+  MOZ_DEFINE_MALLOC_SIZE_OF(MallocSizeOf)
+
+ public:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_NSIMEMORYREPORTER
+
+  // Blob constructor.
+  static already_AddRefed<StreamBlobImpl> Create(
+      already_AddRefed<nsIInputStream> aInputStream,
+      const nsAString& aContentType, uint64_t aLength,
+      const nsAString& aBlobImplType);
+
+  // File constructor.
+  static already_AddRefed<StreamBlobImpl> Create(
+      already_AddRefed<nsIInputStream> aInputStream, const nsAString& aName,
+      const nsAString& aContentType, int64_t aLastModifiedDate,
+      uint64_t aLength, const nsAString& aBlobImplType);
+
+  void CreateInputStream(nsIInputStream** aStream,
+                         ErrorResult& aRv) const override;
+
+  already_AddRefed<BlobImpl> CreateSlice(uint64_t aStart, uint64_t aLength,
+                                         const nsAString& aContentType,
+                                         ErrorResult& aRv) const override;
+
+  bool IsMemoryFile() const override { return true; }
+
+  int64_t GetFileId() const override { return mFileId; }
+
+  void SetFileId(int64_t aFileId) { mFileId = aFileId; }
+
+  void SetFullPath(const nsAString& aFullPath) { mFullPath = aFullPath; }
+
+  void GetMozFullPathInternal(nsAString& aFullPath, ErrorResult& aRv) override {
+    aFullPath = mFullPath;
+  }
+
+  void SetIsDirectory(bool aIsDirectory) { mIsDirectory = aIsDirectory; }
+
+  bool IsDirectory() const override { return mIsDirectory; }
+
+  size_t GetAllocationSize() const override;
+
+  size_t GetAllocationSize(
+      FallibleTArray<BlobImpl*>& aVisitedBlobImpls) const override {
+    return GetAllocationSize();
+  }
+
+  void GetBlobImplType(nsAString& aBlobImplType) const override;
+
+ private:
+  // Blob constructor.
+  StreamBlobImpl(already_AddRefed<nsICloneableInputStream> aInputStream,
+                 const nsAString& aContentType, uint64_t aLength,
+                 const nsAString& aBlobImplType);
+
+  // File constructor.
+  StreamBlobImpl(already_AddRefed<nsICloneableInputStream> aInputStream,
+                 const nsAString& aName, const nsAString& aContentType,
+                 int64_t aLastModifiedDate, uint64_t aLength,
+                 const nsAString& aBlobImplType);
+
+  ~StreamBlobImpl() override;
+
+  void MaybeRegisterMemoryReporter();
+
+  nsCOMPtr<nsICloneableInputStream> mInputStream;
+
+  nsString mBlobImplType;
+
+  nsString mFullPath;
+  bool mIsDirectory;
+  int64_t mFileId;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_StreamBlobImpl_h
diff --git a/dom/file/StringBlobImpl.cpp b/dom/file/StringBlobImpl.cpp
new file mode 100644
index 0000000000..8cb657ca5f
--- /dev/null
+++ b/dom/file/StringBlobImpl.cpp
@@ -0,0 +1,51 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "StringBlobImpl.h"
+#include "nsStringStream.h"
+
+namespace mozilla::dom {
+
+NS_IMPL_ISUPPORTS_INHERITED(StringBlobImpl, BlobImpl, nsIMemoryReporter)
+
+/* static */
+already_AddRefed<StringBlobImpl> StringBlobImpl::Create(
+    const nsACString& aData, const nsAString& aContentType) {
+  RefPtr<StringBlobImpl> blobImpl = new StringBlobImpl(aData, aContentType);
+  RegisterWeakMemoryReporter(blobImpl);
+  return blobImpl.forget();
+}
+
+StringBlobImpl::StringBlobImpl(const nsACString& aData,
+                               const nsAString& aContentType)
+    : BaseBlobImpl(aContentType, aData.Length()), mData(aData) {}
+
+StringBlobImpl::~StringBlobImpl() { UnregisterWeakMemoryReporter(this); }
+
+already_AddRefed<BlobImpl> StringBlobImpl::CreateSlice(
+    uint64_t aStart, uint64_t aLength, const nsAString& aContentType,
+    ErrorResult& aRv) const {
+  RefPtr<BlobImpl> impl =
+      new StringBlobImpl(Substring(mData, aStart, aLength), aContentType);
+  return impl.forget();
+}
+
+void StringBlobImpl::CreateInputStream(nsIInputStream** aStream,
+                                       ErrorResult& aRv) const {
+  aRv = NS_NewCStringInputStream(aStream, mData);
+}
+
+NS_IMETHODIMP
+StringBlobImpl::CollectReports(nsIHandleReportCallback* aHandleReport,
+                               nsISupports* aData, bool aAnonymize) {
+  MOZ_COLLECT_REPORT("explicit/dom/memory-file-data/string", KIND_HEAP,
+                     UNITS_BYTES,
+                     mData.SizeOfExcludingThisIfUnshared(MallocSizeOf),
+                     "Memory used to back a File/Blob based on a string.");
+  return NS_OK;
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/StringBlobImpl.h b/dom/file/StringBlobImpl.h
new file mode 100644
index 0000000000..3b3037e693
--- /dev/null
+++ b/dom/file/StringBlobImpl.h
@@ -0,0 +1,53 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_StringBlobImpl_h
+#define mozilla_dom_StringBlobImpl_h
+
+#include "BaseBlobImpl.h"
+#include "nsIMemoryReporter.h"
+
+namespace mozilla::dom {
+
+class StringBlobImpl final : public BaseBlobImpl, public nsIMemoryReporter {
+  MOZ_DEFINE_MALLOC_SIZE_OF(MallocSizeOf)
+
+ public:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_NSIMEMORYREPORTER
+
+  static already_AddRefed<StringBlobImpl> Create(const nsACString& aData,
+                                                 const nsAString& aContentType);
+
+  void CreateInputStream(nsIInputStream** aStream,
+                         ErrorResult& aRv) const override;
+
+  already_AddRefed<BlobImpl> CreateSlice(uint64_t aStart, uint64_t aLength,
+                                         const nsAString& aContentType,
+                                         ErrorResult& aRv) const override;
+
+  size_t GetAllocationSize() const override { return mData.Length(); }
+
+  size_t GetAllocationSize(
+      FallibleTArray<BlobImpl*>& aVisitedBlobImpls) const override {
+    return GetAllocationSize();
+  }
+
+  void GetBlobImplType(nsAString& aBlobImplType) const override {
+    aBlobImplType = u"StringBlobImpl"_ns;
+  }
+
+ private:
+  StringBlobImpl(const nsACString& aData, const nsAString& aContentType);
+
+  ~StringBlobImpl() override;
+
+  nsCString mData;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_StringBlobImpl_h
diff --git a/dom/file/TemporaryFileBlobImpl.cpp b/dom/file/TemporaryFileBlobImpl.cpp
new file mode 100644
index 0000000000..505d4a96d4
--- /dev/null
+++ b/dom/file/TemporaryFileBlobImpl.cpp
@@ -0,0 +1,126 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "TemporaryFileBlobImpl.h"
+
+#include "RemoteLazyInputStreamThread.h"
+#include "mozilla/ErrorResult.h"
+#include "nsFileStreams.h"
+#include "nsIFile.h"
+#include "nsIFileStreams.h"
+#include "nsNetUtil.h"
+#include "nsThreadUtils.h"
+#include "nsXULAppAPI.h"
+
+using namespace mozilla::ipc;
+
+namespace mozilla::dom {
+
+namespace {
+
+// Here the flags needed in order to keep the temporary file opened.
+// 1. REOPEN_ON_REWIND -> otherwise the stream is not serializable more than
+//                        once.
+// 2. no DEFER_OPEN -> the file must be kept open on windows in order to be
+//                     deleted when used.
+// 3. no CLOSE_ON_EOF -> the file will be closed by the DTOR. No needs. Also
+//                       because the inputStream will not be read directly.
+// 4. no SHARE_DELETE -> We don't want to allow this file to be deleted.
+const uint32_t sTemporaryFileStreamFlags = nsIFileInputStream::REOPEN_ON_REWIND;
+
+class TemporaryFileInputStream final : public nsFileInputStream {
+ public:
+  static nsresult Create(nsIFile* aFile, nsIInputStream** aInputStream) {
+    MOZ_ASSERT(aFile);
+    MOZ_ASSERT(aInputStream);
+    MOZ_ASSERT(XRE_IsParentProcess());
+
+    RefPtr<TemporaryFileInputStream> stream =
+        new TemporaryFileInputStream(aFile);
+
+    nsresult rv = stream->Init(aFile, -1, -1, sTemporaryFileStreamFlags);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    stream.forget(aInputStream);
+    return NS_OK;
+  }
+
+  void Serialize(InputStreamParams& aParams, uint32_t aMaxSize,
+                 uint32_t* aSizeUsed) override {
+    MOZ_CRASH("This inputStream cannot be serialized.");
+  }
+
+  bool Deserialize(const InputStreamParams& aParams) override {
+    MOZ_CRASH("This inputStream cannot be deserialized.");
+    return false;
+  }
+
+ private:
+  explicit TemporaryFileInputStream(nsIFile* aFile) : mFile(aFile) {
+    MOZ_ASSERT(XRE_IsParentProcess());
+  }
+
+  ~TemporaryFileInputStream() override {
+    // Let's delete the file on the RemoteLazyInputStream Thread.
+    RefPtr<RemoteLazyInputStreamThread> thread =
+        RemoteLazyInputStreamThread::GetOrCreate();
+    if (NS_WARN_IF(!thread)) {
+      return;
+    }
+
+    nsCOMPtr<nsIFile> file = std::move(mFile);
+    thread->Dispatch(
+        NS_NewRunnableFunction("TemporaryFileInputStream::Runnable",
+                               [file]() { file->Remove(false); }));
+  }
+
+  nsCOMPtr<nsIFile> mFile;
+};
+
+}  // namespace
+
+TemporaryFileBlobImpl::TemporaryFileBlobImpl(nsIFile* aFile,
+                                             const nsAString& aContentType)
+    : FileBlobImpl(aFile, u""_ns, aContentType)
+#ifdef DEBUG
+      ,
+      mInputStreamCreated(false)
+#endif
+{
+  MOZ_ASSERT(XRE_IsParentProcess());
+
+  // This must be considered a blob.
+  mIsFile = false;
+}
+
+TemporaryFileBlobImpl::~TemporaryFileBlobImpl() {
+  MOZ_ASSERT(mInputStreamCreated);
+}
+
+already_AddRefed<BlobImpl> TemporaryFileBlobImpl::CreateSlice(
+    uint64_t aStart, uint64_t aLength, const nsAString& aContentType,
+    ErrorResult& aRv) const {
+  MOZ_CRASH("This BlobImpl is not meant to be sliced!");
+  return nullptr;
+}
+
+void TemporaryFileBlobImpl::CreateInputStream(nsIInputStream** aStream,
+                                              ErrorResult& aRv) const {
+#ifdef DEBUG
+  MOZ_ASSERT(!mInputStreamCreated);
+  // CreateInputStream can be called only once.
+  mInputStreamCreated = true;
+#endif
+
+  aRv = TemporaryFileInputStream::Create(mFile, aStream);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/TemporaryFileBlobImpl.h b/dom/file/TemporaryFileBlobImpl.h
new file mode 100644
index 0000000000..d11c67f955
--- /dev/null
+++ b/dom/file/TemporaryFileBlobImpl.h
@@ -0,0 +1,47 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_TemporaryFileBlobImpl_h
+#define mozilla_dom_TemporaryFileBlobImpl_h
+
+#include "FileBlobImpl.h"
+
+namespace mozilla::dom {
+
+// This class is meant to be used by TemporaryIPCBlobParent only.
+// Don't use it for anything else, please!
+// Note that CreateInputStream() _must_ be called, and called just once!
+
+// This class is a BlobImpl because it needs to be sent via IPC using
+// IPCBlobUtils.
+class TemporaryFileBlobImpl final : public FileBlobImpl {
+#ifdef DEBUG
+  mutable bool mInputStreamCreated;
+#endif
+
+ public:
+  explicit TemporaryFileBlobImpl(nsIFile* aFile, const nsAString& aContentType);
+
+  // Overrides
+  void CreateInputStream(nsIInputStream** aStream,
+                         ErrorResult& aRv) const override;
+
+  void GetBlobImplType(nsAString& aBlobImplType) const override {
+    aBlobImplType = u"TemporaryFileBlobImpl"_ns;
+  }
+
+ protected:
+  ~TemporaryFileBlobImpl() override;
+
+ private:
+  already_AddRefed<BlobImpl> CreateSlice(uint64_t aStart, uint64_t aLength,
+                                         const nsAString& aContentType,
+                                         ErrorResult& aRv) const override;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_TemporaryFileBlobImpl_h
diff --git a/dom/file/ipc/FileCreatorChild.cpp b/dom/file/ipc/FileCreatorChild.cpp
new file mode 100644
index 0000000000..95ac19f17b
--- /dev/null
+++ b/dom/file/ipc/FileCreatorChild.cpp
@@ -0,0 +1,59 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "FileCreatorChild.h"
+#include "mozilla/dom/BlobImpl.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/dom/IPCBlobUtils.h"
+
+namespace mozilla::dom {
+
+FileCreatorChild::FileCreatorChild() = default;
+
+FileCreatorChild::~FileCreatorChild() { MOZ_ASSERT(!mPromise); }
+
+void FileCreatorChild::SetPromise(Promise* aPromise) {
+  MOZ_ASSERT(aPromise);
+  MOZ_ASSERT(!mPromise);
+
+  mPromise = aPromise;
+}
+
+mozilla::ipc::IPCResult FileCreatorChild::Recv__delete__(
+    const FileCreationResult& aResult) {
+  MOZ_ASSERT(mPromise);
+
+  RefPtr<Promise> promise;
+  promise.swap(mPromise);
+
+  if (aResult.type() == FileCreationResult::TFileCreationErrorResult) {
+    promise->MaybeReject(aResult.get_FileCreationErrorResult().errorCode());
+    return IPC_OK();
+  }
+
+  MOZ_ASSERT(aResult.type() == FileCreationResult::TFileCreationSuccessResult);
+
+  RefPtr<dom::BlobImpl> impl = dom::IPCBlobUtils::Deserialize(
+      aResult.get_FileCreationSuccessResult().blob());
+
+  RefPtr<File> file = File::Create(promise->GetParentObject(), impl);
+  if (NS_WARN_IF(!file)) {
+    promise->MaybeReject(NS_ERROR_FAILURE);
+    return IPC_OK();
+  }
+
+  promise->MaybeResolve(file);
+  return IPC_OK();
+}
+
+void FileCreatorChild::ActorDestroy(ActorDestroyReason aWhy) {
+  if (mPromise) {
+    mPromise->MaybeReject(NS_ERROR_FAILURE);
+    mPromise = nullptr;
+  }
+};
+
+}  // namespace mozilla::dom
diff --git a/dom/file/ipc/FileCreatorChild.h b/dom/file/ipc/FileCreatorChild.h
new file mode 100644
index 0000000000..eb5dc09d92
--- /dev/null
+++ b/dom/file/ipc/FileCreatorChild.h
@@ -0,0 +1,33 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_FileCreatorChild_h
+#define mozilla_dom_FileCreatorChild_h
+
+#include "mozilla/dom/PFileCreatorChild.h"
+
+namespace mozilla::dom {
+
+class FileCreatorChild final : public mozilla::dom::PFileCreatorChild {
+  friend class mozilla::dom::PFileCreatorChild;
+
+ public:
+  FileCreatorChild();
+  ~FileCreatorChild() override;
+
+  void SetPromise(Promise* aPromise);
+
+ private:
+  mozilla::ipc::IPCResult Recv__delete__(const FileCreationResult& aResult);
+
+  void ActorDestroy(ActorDestroyReason aWhy) override;
+
+  RefPtr<Promise> mPromise;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_FileCreatorChild_h
diff --git a/dom/file/ipc/FileCreatorParent.cpp b/dom/file/ipc/FileCreatorParent.cpp
new file mode 100644
index 0000000000..8a3f316390
--- /dev/null
+++ b/dom/file/ipc/FileCreatorParent.cpp
@@ -0,0 +1,136 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "FileCreatorParent.h"
+#include "mozilla/dom/FileBlobImpl.h"
+#include "mozilla/dom/IPCBlobUtils.h"
+#include "mozilla/dom/MultipartBlobImpl.h"
+#include "nsIFile.h"
+
+namespace mozilla::dom {
+
+FileCreatorParent::FileCreatorParent()
+    : mBackgroundEventTarget(GetCurrentEventTarget()), mIPCActive(true) {}
+
+FileCreatorParent::~FileCreatorParent() = default;
+
+mozilla::ipc::IPCResult FileCreatorParent::CreateAndShareFile(
+    const nsAString& aFullPath, const nsAString& aType, const nsAString& aName,
+    const Maybe<int64_t>& aLastModified, const bool& aExistenceCheck,
+    const bool& aIsFromNsIFile) {
+  RefPtr<dom::BlobImpl> blobImpl;
+  nsresult rv =
+      CreateBlobImpl(aFullPath, aType, aName, aLastModified.isSome(),
+                     aLastModified.isSome() ? aLastModified.value() : 0,
+                     aExistenceCheck, aIsFromNsIFile, getter_AddRefs(blobImpl));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    Unused << Send__delete__(this, FileCreationErrorResult(rv));
+    return IPC_OK();
+  }
+
+  MOZ_ASSERT(blobImpl);
+
+  // FileBlobImpl is unable to return the correct type on this thread because
+  // nsIMIMEService is not thread-safe. We must exec the 'type' getter on
+  // main-thread before send the blob to the child actor.
+
+  RefPtr<FileCreatorParent> self = this;
+  NS_DispatchToMainThread(NS_NewRunnableFunction(
+      "FileCreatorParent::CreateAndShareFile", [self, blobImpl]() {
+        nsAutoString type;
+        blobImpl->GetType(type);
+
+        self->mBackgroundEventTarget->Dispatch(NS_NewRunnableFunction(
+            "FileCreatorParent::CreateAndShareFile return", [self, blobImpl]() {
+              if (self->mIPCActive) {
+                IPCBlob ipcBlob;
+                nsresult rv = dom::IPCBlobUtils::Serialize(blobImpl, ipcBlob);
+                if (NS_WARN_IF(NS_FAILED(rv))) {
+                  Unused << Send__delete__(self, FileCreationErrorResult(rv));
+                  return;
+                }
+
+                Unused << Send__delete__(self,
+                                         FileCreationSuccessResult(ipcBlob));
+              }
+            }));
+      }));
+
+  return IPC_OK();
+}
+
+void FileCreatorParent::ActorDestroy(ActorDestroyReason aWhy) {
+  mIPCActive = false;
+}
+
+/* static */
+nsresult FileCreatorParent::CreateBlobImpl(
+    const nsAString& aPath, const nsAString& aType, const nsAString& aName,
+    bool aLastModifiedPassed, int64_t aLastModified, bool aExistenceCheck,
+    bool aIsFromNsIFile, BlobImpl** aBlobImpl) {
+  MOZ_ASSERT(!NS_IsMainThread());
+
+  nsCOMPtr<nsIFile> file;
+  nsresult rv = NS_NewLocalFile(aPath, true, getter_AddRefs(file));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  bool exists;
+  rv = file->Exists(&exists);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  if (aExistenceCheck) {
+    if (!exists) {
+      return NS_ERROR_FILE_NOT_FOUND;
+    }
+
+    bool isDir;
+    rv = file->IsDirectory(&isDir);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    if (isDir) {
+      return NS_ERROR_FILE_IS_DIRECTORY;
+    }
+  }
+
+  RefPtr<FileBlobImpl> impl = new FileBlobImpl(file);
+
+  // If the file doesn't exist, we cannot have its path, its size and so on.
+  // Let's set them now.
+  if (!exists) {
+    MOZ_ASSERT(!aExistenceCheck);
+
+    impl->SetMozFullPath(aPath);
+    impl->SetLastModified(0);
+    impl->SetEmptySize();
+  }
+
+  if (!aName.IsEmpty()) {
+    impl->SetName(aName);
+  }
+
+  if (!aType.IsEmpty()) {
+    impl->SetType(aType);
+  }
+
+  if (aLastModifiedPassed) {
+    impl->SetLastModified(aLastModified);
+  }
+
+  if (!aIsFromNsIFile) {
+    impl->SetMozFullPath(u""_ns);
+  }
+
+  impl.forget(aBlobImpl);
+  return NS_OK;
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/ipc/FileCreatorParent.h b/dom/file/ipc/FileCreatorParent.h
new file mode 100644
index 0000000000..f43dbee886
--- /dev/null
+++ b/dom/file/ipc/FileCreatorParent.h
@@ -0,0 +1,45 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_FileCreatorParent_h
+#define mozilla_dom_FileCreatorParent_h
+
+#include "mozilla/dom/PFileCreatorParent.h"
+
+class nsIFile;
+
+namespace mozilla::dom {
+
+class BlobImpl;
+
+class FileCreatorParent final : public mozilla::dom::PFileCreatorParent {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(FileCreatorParent)
+
+  FileCreatorParent();
+
+  mozilla::ipc::IPCResult CreateAndShareFile(
+      const nsAString& aFullPath, const nsAString& aType,
+      const nsAString& aName, const Maybe<int64_t>& aLastModified,
+      const bool& aExistenceCheck, const bool& aIsFromNsIFile);
+
+ private:
+  ~FileCreatorParent() override;
+
+  void ActorDestroy(ActorDestroyReason aWhy) override;
+
+  nsresult CreateBlobImpl(const nsAString& aPath, const nsAString& aType,
+                          const nsAString& aName, bool aLastModifiedPassed,
+                          int64_t aLastModified, bool aExistenceCheck,
+                          bool aIsFromNsIFile, BlobImpl** aBlobImpl);
+
+  nsCOMPtr<nsIEventTarget> mBackgroundEventTarget;
+  bool mIPCActive;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_FileCreatorParent_h
diff --git a/dom/file/ipc/IPCBlob.ipdlh b/dom/file/ipc/IPCBlob.ipdlh
new file mode 100644
index 0000000000..08c6b50a8d
--- /dev/null
+++ b/dom/file/ipc/IPCBlob.ipdlh
@@ -0,0 +1,56 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+include IPCStream;
+include ProtocolTypes;
+
+using struct mozilla::void_t from "mozilla/ipc/IPCCore.h";
+[RefCounted] using class mozilla::RemoteLazyInputStream from "mozilla/RemoteLazyInputStream.h";
+
+namespace mozilla {
+
+union RemoteLazyStream
+{
+  // Parent to Child: The child will receive a RemoteLazyInputStream. Nothing
+  // can be done with it except retrieving the size.
+  RemoteLazyInputStream;
+
+  // Child to Parent: Normal serialization.
+  IPCStream;
+};
+
+namespace dom {
+
+// This contains any extra bit for making a File out of a Blob.
+// For more information about Blobs and IPC, please read the comments in
+// IPCBlobUtils.h
+
+struct IPCFile
+{
+  nsString name;
+  int64_t lastModified;
+  nsString DOMPath;
+  nsString fullPath;
+
+  // Useful for Entries API.
+  bool isDirectory;
+};
+
+struct IPCBlob
+{
+  nsString type;
+  uint64_t size;
+  nsString blobImplType;
+
+  RemoteLazyStream inputStream;
+
+  // Nothing is for Blob
+  IPCFile? file;
+
+  // This ID is used only by indexedDB tests.
+  int64_t fileId;
+};
+
+} // namespace dom
+} // namespace mozilla
diff --git a/dom/file/ipc/IPCBlobUtils.cpp b/dom/file/ipc/IPCBlobUtils.cpp
new file mode 100644
index 0000000000..78409da529
--- /dev/null
+++ b/dom/file/ipc/IPCBlobUtils.cpp
@@ -0,0 +1,179 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "IPCBlobUtils.h"
+#include "RemoteLazyInputStream.h"
+#include "RemoteLazyInputStreamChild.h"
+#include "RemoteLazyInputStreamParent.h"
+#include "mozilla/dom/IPCBlob.h"
+#include "mozilla/ipc/BackgroundParent.h"
+#include "mozilla/ipc/PBackgroundParent.h"
+#include "mozilla/ipc/PBackgroundChild.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/ipc/IPCStreamUtils.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+#include "RemoteLazyInputStreamStorage.h"
+#include "StreamBlobImpl.h"
+#include "prtime.h"
+
+namespace mozilla::dom::IPCBlobUtils {
+
+already_AddRefed<BlobImpl> Deserialize(const IPCBlob& aIPCBlob) {
+  nsCOMPtr<nsIInputStream> inputStream;
+
+  const RemoteLazyStream& stream = aIPCBlob.inputStream();
+  switch (stream.type()) {
+    // Parent to child: when an nsIInputStream is sent from parent to child, the
+    // child receives a RemoteLazyInputStream actor.
+    case RemoteLazyStream::TRemoteLazyInputStream: {
+      inputStream = stream.get_RemoteLazyInputStream();
+      break;
+    }
+
+    // Child to Parent: when a blob is created on the content process send it's
+    // sent to the parent, we have an IPCStream object.
+    case RemoteLazyStream::TIPCStream:
+      MOZ_ASSERT(XRE_IsParentProcess());
+      inputStream = DeserializeIPCStream(stream.get_IPCStream());
+      break;
+
+    default:
+      MOZ_CRASH("Unknown type.");
+      break;
+  }
+
+  MOZ_ASSERT(inputStream);
+
+  RefPtr<StreamBlobImpl> blobImpl;
+
+  if (aIPCBlob.file().isNothing()) {
+    blobImpl = StreamBlobImpl::Create(inputStream.forget(), aIPCBlob.type(),
+                                      aIPCBlob.size(), aIPCBlob.blobImplType());
+  } else {
+    const IPCFile& file = aIPCBlob.file().ref();
+    blobImpl = StreamBlobImpl::Create(inputStream.forget(), file.name(),
+                                      aIPCBlob.type(), file.lastModified(),
+                                      aIPCBlob.size(), aIPCBlob.blobImplType());
+    blobImpl->SetDOMPath(file.DOMPath());
+    blobImpl->SetFullPath(file.fullPath());
+    blobImpl->SetIsDirectory(file.isDirectory());
+  }
+
+  blobImpl->SetFileId(aIPCBlob.fileId());
+
+  return blobImpl.forget();
+}
+
+nsresult Serialize(BlobImpl* aBlobImpl, IPCBlob& aIPCBlob) {
+  MOZ_ASSERT(aBlobImpl);
+
+  nsAutoString value;
+  aBlobImpl->GetType(value);
+  aIPCBlob.type() = value;
+
+  aBlobImpl->GetBlobImplType(value);
+  aIPCBlob.blobImplType() = value;
+
+  ErrorResult rv;
+  aIPCBlob.size() = aBlobImpl->GetSize(rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    return rv.StealNSResult();
+  }
+
+  if (!aBlobImpl->IsFile()) {
+    aIPCBlob.file() = Nothing();
+  } else {
+    IPCFile file;
+
+    aBlobImpl->GetName(value);
+    file.name() = value;
+
+    file.lastModified() = aBlobImpl->GetLastModified(rv) * PR_USEC_PER_MSEC;
+    if (NS_WARN_IF(rv.Failed())) {
+      return rv.StealNSResult();
+    }
+
+    aBlobImpl->GetDOMPath(value);
+    file.DOMPath() = value;
+
+    aBlobImpl->GetMozFullPathInternal(value, rv);
+    if (NS_WARN_IF(rv.Failed())) {
+      return rv.StealNSResult();
+    }
+    file.fullPath() = value;
+
+    file.isDirectory() = aBlobImpl->IsDirectory();
+
+    aIPCBlob.file() = Some(file);
+  }
+
+  aIPCBlob.fileId() = aBlobImpl->GetFileId();
+
+  nsCOMPtr<nsIInputStream> inputStream;
+  aBlobImpl->CreateInputStream(getter_AddRefs(inputStream), rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    return rv.StealNSResult();
+  }
+
+  if (XRE_IsParentProcess()) {
+    RefPtr<RemoteLazyInputStream> stream =
+        RemoteLazyInputStream::WrapStream(inputStream);
+    if (NS_WARN_IF(!stream)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    aIPCBlob.inputStream() = stream;
+    return NS_OK;
+  }
+
+  mozilla::ipc::IPCStream stream;
+  if (!mozilla::ipc::SerializeIPCStream(inputStream.forget(), stream,
+                                        /* aAllowLazy */ true)) {
+    return NS_ERROR_FAILURE;
+  }
+  aIPCBlob.inputStream() = stream;
+  return NS_OK;
+}
+
+}  // namespace mozilla::dom::IPCBlobUtils
+
+namespace IPC {
+
+void ParamTraits<mozilla::dom::BlobImpl*>::Write(
+    IPC::MessageWriter* aWriter, mozilla::dom::BlobImpl* aParam) {
+  nsresult rv;
+  mozilla::dom::IPCBlob ipcblob;
+  if (aParam) {
+    rv = mozilla::dom::IPCBlobUtils::Serialize(aParam, ipcblob);
+  }
+  if (!aParam || NS_WARN_IF(NS_FAILED(rv))) {
+    WriteParam(aWriter, false);
+  } else {
+    WriteParam(aWriter, true);
+    WriteParam(aWriter, ipcblob);
+  }
+}
+
+bool ParamTraits<mozilla::dom::BlobImpl*>::Read(
+    IPC::MessageReader* aReader, RefPtr<mozilla::dom::BlobImpl>* aResult) {
+  *aResult = nullptr;
+
+  bool notnull = false;
+  if (!ReadParam(aReader, &notnull)) {
+    return false;
+  }
+  if (notnull) {
+    mozilla::dom::IPCBlob ipcblob;
+    if (!ReadParam(aReader, &ipcblob)) {
+      return false;
+    }
+    *aResult = mozilla::dom::IPCBlobUtils::Deserialize(ipcblob);
+  }
+  return true;
+}
+
+}  // namespace IPC
diff --git a/dom/file/ipc/IPCBlobUtils.h b/dom/file/ipc/IPCBlobUtils.h
new file mode 100644
index 0000000000..17fce3195a
--- /dev/null
+++ b/dom/file/ipc/IPCBlobUtils.h
@@ -0,0 +1,268 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_IPCBlobUtils_h
+#define mozilla_dom_IPCBlobUtils_h
+
+#include "mozilla/RefPtr.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/ipc/IPDLParamTraits.h"
+
+/*
+ * Blobs and IPC
+ * ~~~~~~~~~~~~~
+ *
+ * Simplifying, DOM Blob objects are chunks of data with a content type and a
+ * size. DOM Files are Blobs with a name. They are are used in many APIs and
+ * they can be cloned and sent cross threads and cross processes.
+ *
+ * If we see Blobs from a platform point of view, the main (and often, the only)
+ * interesting part is how to retrieve data from it. This is done via
+ * nsIInputStream and, except for a couple of important details, this stream is
+ * used in the parent process.
+ *
+ * For this reason, when we consider the serialization of a blob via IPC
+ * messages, the biggest effort is put in how to manage the nsInputStream
+ * correctly. To serialize, we use the IPCBlob data struct: basically, the blob
+ * properties (size, type, name if it's a file) and the nsIInputStream.
+ *
+ * Before talking about the nsIInputStream it's important to say that we have
+ * different kinds of Blobs, based on the different kinds of sources. A non
+ * exaustive list is:
+ * - a memory buffer: MemoryBlobImpl
+ * - a string: StringBlobImpl
+ * - a real OS file: FileBlobImpl
+ * - a generic nsIInputStream: StreamBlobImpl
+ * - an empty blob: EmptyBlobImpl
+ * - more blobs combined together: MultipartBlobImpl
+ * Each one of these implementations has a custom ::CreateInputStream method.
+ * So, basically, each one has a different kind of nsIInputStream (nsFileStream,
+ * nsIStringInputStream, SlicedInputStream, and so on).
+ *
+ * Another important point to keep in mind is that a Blob can be created on the
+ * content process (for example: |new Blob([123])|) or it can be created on the
+ * parent process and sent to content (a FilePicker creates Blobs and it runs on
+ * the parent process).
+ *
+ * DocumentLoadListener uses blobs to serialize the POST data back to the
+ * content process (for insertion into session history). This lets it correctly
+ * handle OS files by reference, and avoid copying the underlying buffer data
+ * unless it is read. This can hopefully be removed once SessionHistory is
+ * handled in the parent process.
+ *
+ * Child to Parent Blob Serialization
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * When a document creates a blob, this can be sent, for different reasons to
+ * the parent process. For instance it can be sent as part of a FormData, or it
+ * can be converted to a BlobURL and broadcasted to any other existing
+ * processes.
+ *
+ * When this happens, we use the IPCStream data struct for the serialization
+ * of the nsIInputStream. This means that, if the stream is fully serializable
+ * and its size is lower than 1Mb, we are able to recreate the stream completely
+ * on the parent side. This happens, basically with any kind of child-to-parent
+ * stream except for huge memory streams. In this case we end up using
+ * DataPipe. See more information in IPCStreamUtils.h.
+ *
+ * In order to populate IPCStream correctly, we use SerializeIPCStream as
+ * documented in IPCStreamUtils.h.
+ *
+ * Parent to Child Blob Serialization
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * This scenario is common when we talk about Blobs pointing to real files:
+ * HTMLInputElement (type=file), or Entries API, DataTransfer and so on. But we
+ * also have this scenario when a content process creates a Blob and it
+ * broadcasts it because of a BlobURL or because BroadcastChannel API is used.
+ *
+ * The approach here is this: normally, the content process doesn't really read
+ * data from the blob nsIInputStream. The content process needs to have the
+ * nsIInputStream and be able to send it back to the parent process when the
+ * "real" work needs to be done. This is true except for 2 usecases: FileReader
+ * API and BlobURL usage. So, if we ignore these 2, normally, the parent sends a
+ * blob nsIInputStream to a content process, and then, it will receive it back
+ * in order to do some networking, or whatever.
+ *
+ * For this reason, IPCBlobUtils uses a particular protocol for serializing
+ * nsIInputStream parent to child: PRemoteLazyInputStream. This protocol keeps
+ * the original nsIInputStream alive on the parent side, and gives its size and
+ * a UUID to the child side. The child side creates a RemoteLazyInputStream and
+ * that is incapsulated into a StreamBlobImpl.
+ *
+ * The UUID is useful when the content process sends the same nsIInputStream
+ * back to the parent process because, the only information it has to share is
+ * the UUID. Each nsIInputStream sent via PRemoteLazyInputStream, is registered
+ * into the RemoteLazyInputStreamStorage.
+ *
+ * On the content process side, RemoteLazyInputStream is a special inputStream:
+ * the only reliable methods are:
+ * - nsIInputStream.available() - the size is shared by PRemoteLazyInputStream
+ *   actor.
+ * - nsIIPCSerializableInputStream.serialize() - we can give back this stream to
+ *   the parent because we know its UUID.
+ * - nsICloneableInputStream.cloneable() and nsICloneableInputStream.clone() -
+ *   this stream can be cloned. We just need to have a reference of the
+ *   PRemoteLazyInputStream actor and its UUID.
+ * - nsIAsyncInputStream.asyncWait() - see next section.
+ *
+ * Any other method (read, readSegment and so on) will fail if asyncWait() is
+ * not previously called (see the next section). Basically, this inputStream
+ * cannot be used synchronously for any 'real' reading operation.
+ *
+ * When the parent receives the serialization of a RemoteLazyInputStream, it is
+ * able to retrieve the correct nsIInputStream using the UUID and
+ * RemoteLazyInputStreamStorage.
+ *
+ * Parent to Child Streams, FileReader and BlobURL
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * The FileReader and BlobURL scenarios are described here.
+ *
+ * When content process needs to read data from a Blob sent from the parent
+ * process, it must do it asynchronously using RemoteLazyInputStream as a
+ * nsIAsyncInputStream stream. This happens calling
+ * RemoteLazyInputStream.asyncWait(). At that point, the child actor will send a
+ * StreamNeeded() IPC message to the parent side. When this is received, the
+ * parent retrieves the 'real' stream from RemoteLazyInputStreamStorage using
+ * the UUID, it will serialize the 'real' stream, and it will send it to the
+ * child side.
+ *
+ * When the 'real' stream is received (RecvStreamReady()), the asyncWait
+ * callback will be executed and, from that moment, any RemoteLazyInputStream
+ * method will be forwarded to the 'real' stream ones. This means that the
+ * reading will be available.
+ *
+ * RemoteLazyInputStream Thread
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * RemoteLazyInputStreamChild actor can be created in any thread (sort of) and
+ * their top-level IPDL protocol is PBackground. These actors are wrapped by 1
+ * or more RemoteLazyInputStream objects in order to expose nsIInputStream
+ * interface and be thread-safe.
+ *
+ * But IPDL actors are not thread-safe and any SendFoo() method must be executed
+ * on the owning thread. This means that this thread must be kept alive for the
+ * life-time of the RemoteLazyInputStream.
+ *
+ * In doing this, there are 2 main issues:
+ * a. if a remote Blob is created on a worker (because of a
+ *    BroadcastChannel/MessagePort for instance) and it sent to the main-thread
+ *    via PostMessage(), we have to keep that worker alive.
+ * b. if the remote Blob is created on the main-thread, any SendFoo() has to be
+ *    executed on the main-thread. This is true also when the inputStream is
+ *    used on another thread (note that nsIInputStream could do I/O and usually
+ *    they are used on special I/O threads).
+ *
+ * In order to avoid this, RemoteLazyInputStreamChild are 'migrated' to a
+ * DOM-File thread. This is done in this way:
+ *
+ * 1. If RemoteLazyInputStreamChild actor is not already owned by DOM-File
+ *    thread, it calls Send__delete__ in order to inform the parent side that we
+ *    don't need this IPC channel on the current thread.
+ * 2. A new RemoteLazyInputStreamChild is created. RemoteLazyInputStreamThread
+ *    is used to assign this actor to the DOM-File thread.
+ *    RemoteLazyInputStreamThread::GetOrCreate() creates the DOM-File thread if
+ *    it doesn't exist yet. Pending operations and RemoteLazyInputStreams are
+ *    moved onto the new actor.
+ * 3. RemoteLazyInputStreamParent::Recv__delete__ is called on the parent side
+ *    and the parent actor is deleted. Doing this we don't remove the UUID from
+ *    RemoteLazyInputStreamStorage.
+ * 4. The RemoteLazyInputStream constructor is sent with the new
+ *    RemoteLazyInputStreamChild actor, with the DOM-File thread's PBackground
+ *    as its manager.
+ * 5. When the new RemoteLazyInputStreamParent actor is created, it will receive
+ *    the same UUID of the previous parent actor. The nsIInputStream will be
+ *    retrieved from RemoteLazyInputStreamStorage.
+ * 6. In order to avoid leaks, RemoteLazyInputStreamStorage will monitor child
+ *    processes and in case one of them dies, it will release the
+ *    nsIInputStream objects belonging to that process.
+ *
+ * If any API wants to retrieve a 'real inputStream when the migration is in
+ * progress, that operation is stored in a pending queue and processed at the
+ * end of the migration.
+ *
+ * IPCBlob and nsIAsyncInputStream
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * RemoteLazyInputStream is always async. If the remote inputStream is not
+ * async, RemoteLazyInputStream will create a pipe stream around it in order to
+ * be consistently async.
+ *
+ * Slicing IPCBlob
+ * ~~~~~~~~~~~~~~~
+ *
+ * Normally, slicing a blob consists of the creation of a new Blob, with a
+ * SlicedInputStream() wrapping a clone of the original inputStream. But this
+ * approach is extremely inefficient with IPCBlob, because it could be that we
+ * wrap the pipe stream and not the remote inputStream (See the previous section
+ * of this documentation). If we end up doing so, also if the remote
+ * inputStream is seekable, the pipe will not be, and in order to reach the
+ * starting point, SlicedInputStream will do consecutive read()s.
+ *
+ * This problem is fixed implmenting nsICloneableWithRange in
+ * RemoteLazyInputStream and using cloneWithRange() when a StreamBlobImpl is
+ * sliced. When the remote stream is received, it will be sliced directly.
+ *
+ * If we want to represent the hierarchy of the InputStream classes, instead
+ * of having: |SlicedInputStream(RemoteLazyInputStream(Async
+ * Pipe(RemoteStream)))|, we have: |RemoteLazyInputStream(Async
+ * Pipe(SlicedInputStream(RemoteStream)))|.
+ *
+ * When RemoteLazyInputStream is serialized and sent to the parent process,
+ * start and range are sent too and SlicedInputStream is used in the parent side
+ * as well.
+ *
+ * Socket Process
+ * ~~~~~~~~~~~~~~
+ *
+ * The socket process is a separate process used to do networking operations.
+ * When a website sends a blob as the body of a POST/PUT request, we need to
+ * send the corresponding RemoteLazyInputStream to the socket process.
+ *
+ * This is the only serialization of RemoteLazyInputStream from parent to child
+ * process and it works _only_ for the socket process. Do not expose this
+ * serialization to PContent or PBackground or any other top-level IPDL protocol
+ * without a DOM File peer review!
+ *
+ * The main difference between Socket Process is that DOM-File thread is not
+ * used. Here is a list of reasons:
+ * - DOM-File moves the ownership of the RemoteLazyInputStream actors to
+ *   PBackground, but in the Socket Process we don't have PBackground (yet?)
+ * - Socket Process is a stable process with a simple life-time configuration:
+ *   we can keep the actors on the main-thread because no Workers are involved.
+ */
+
+namespace mozilla::dom {
+
+class IPCBlob;
+
+namespace IPCBlobUtils {
+
+already_AddRefed<BlobImpl> Deserialize(const IPCBlob& aIPCBlob);
+
+nsresult Serialize(BlobImpl* aBlobImpl, IPCBlob& aIPCBlob);
+
+}  // namespace IPCBlobUtils
+}  // namespace mozilla::dom
+
+namespace IPC {
+
+// ParamTraits implementation for BlobImpl. N.B: If the original BlobImpl cannot
+// be successfully serialized, a warning will be produced and a nullptr will be
+// sent over the wire. When Read()-ing a BlobImpl,
+// __always make sure to handle null!__
+template <>
+struct ParamTraits<mozilla::dom::BlobImpl*> {
+  static void Write(IPC::MessageWriter* aWriter,
+                    mozilla::dom::BlobImpl* aParam);
+  static bool Read(IPC::MessageReader* aReader,
+                   RefPtr<mozilla::dom::BlobImpl>* aResult);
+};
+
+}  // namespace IPC
+
+#endif  // mozilla_dom_IPCBlobUtils_h
diff --git a/dom/file/ipc/PFileCreator.ipdl b/dom/file/ipc/PFileCreator.ipdl
new file mode 100644
index 0000000000..d690820906
--- /dev/null
+++ b/dom/file/ipc/PFileCreator.ipdl
@@ -0,0 +1,38 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+include protocol PBackground;
+
+include IPCBlob;
+
+namespace mozilla {
+namespace dom {
+
+struct FileCreationSuccessResult
+{
+  IPCBlob blob;
+};
+
+struct FileCreationErrorResult
+{
+  nsresult errorCode;
+};
+
+union FileCreationResult
+{
+  FileCreationSuccessResult;
+  FileCreationErrorResult;
+};
+
+[ManualDealloc]
+protocol PFileCreator
+{
+  manager PBackground;
+
+child:
+  async __delete__(FileCreationResult aResult);
+};
+
+} // namespace dom 
+} // namespace mozilla
diff --git a/dom/file/ipc/PRemoteLazyInputStream.ipdl b/dom/file/ipc/PRemoteLazyInputStream.ipdl
new file mode 100644
index 0000000000..82fab20cdb
--- /dev/null
+++ b/dom/file/ipc/PRemoteLazyInputStream.ipdl
@@ -0,0 +1,21 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+include IPCStream;
+
+namespace mozilla {
+
+protocol PRemoteLazyInputStream
+{
+parent:
+  async Clone(Endpoint<PRemoteLazyInputStreamParent> aCloneEndpoint);
+
+  async StreamNeeded(uint64_t aStart, uint64_t aLength) returns (IPCStream? stream);
+
+  async LengthNeeded() returns (int64_t length);
+
+  async Goodbye();
+};
+
+} // namespace mozilla
diff --git a/dom/file/ipc/PTemporaryIPCBlob.ipdl b/dom/file/ipc/PTemporaryIPCBlob.ipdl
new file mode 100644
index 0000000000..2645d6fd50
--- /dev/null
+++ b/dom/file/ipc/PTemporaryIPCBlob.ipdl
@@ -0,0 +1,40 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+include protocol PBackground;
+
+include IPCBlob;
+
+namespace mozilla {
+namespace dom {
+
+union IPCBlobOrError
+{
+  IPCBlob;
+  nsresult;
+};
+
+[ManualDealloc]
+protocol PTemporaryIPCBlob
+{
+  manager PBackground;
+
+  // When this actor is created on the child side, the parent will send
+  // immediatelly back a FileDescriptor or a __delete__ in case of error.
+  // When the FileDescriptor is received, the child has to call
+  // OperationDone(). When OperationDone() is received on the parent side, the
+  // parent actor will send a __delete__.
+
+child:
+  async FileDesc(FileDescriptor aFD);
+  async __delete__(IPCBlobOrError aBlobOrError);
+
+parent:
+  async OperationFailed();
+
+  async OperationDone(nsCString aContentType, FileDescriptor aFD);
+};
+
+} // namespace dom
+} // namespace mozilla
diff --git a/dom/file/ipc/RemoteLazyInputStream.cpp b/dom/file/ipc/RemoteLazyInputStream.cpp
new file mode 100644
index 0000000000..726581ae13
--- /dev/null
+++ b/dom/file/ipc/RemoteLazyInputStream.cpp
@@ -0,0 +1,1424 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "RemoteLazyInputStream.h"
+#include "RemoteLazyInputStreamChild.h"
+#include "RemoteLazyInputStreamParent.h"
+#include "chrome/common/ipc_message_utils.h"
+#include "mozilla/ErrorNames.h"
+#include "mozilla/Logging.h"
+#include "mozilla/PRemoteLazyInputStream.h"
+#include "mozilla/ipc/Endpoint.h"
+#include "mozilla/ipc/InputStreamParams.h"
+#include "mozilla/ipc/MessageChannel.h"
+#include "mozilla/ipc/ProtocolMessageUtils.h"
+#include "mozilla/net/SocketProcessParent.h"
+#include "mozilla/SlicedInputStream.h"
+#include "mozilla/NonBlockingAsyncInputStream.h"
+#include "nsIAsyncInputStream.h"
+#include "nsIAsyncOutputStream.h"
+#include "nsID.h"
+#include "nsIInputStream.h"
+#include "nsIPipe.h"
+#include "nsNetUtil.h"
+#include "nsStreamUtils.h"
+#include "nsStringStream.h"
+#include "RemoteLazyInputStreamStorage.h"
+#include "RemoteLazyInputStreamThread.h"
+
+namespace mozilla {
+
+mozilla::LazyLogModule gRemoteLazyStreamLog("RemoteLazyStream");
+
+namespace {
+
+class InputStreamCallbackRunnable final : public DiscardableRunnable {
+ public:
+  // Note that the execution can be synchronous in case the event target is
+  // null.
+  static void Execute(already_AddRefed<nsIInputStreamCallback> aCallback,
+                      already_AddRefed<nsIEventTarget> aEventTarget,
+                      RemoteLazyInputStream* aStream) {
+    RefPtr<InputStreamCallbackRunnable> runnable =
+        new InputStreamCallbackRunnable(std::move(aCallback), aStream);
+
+    nsCOMPtr<nsIEventTarget> target = std::move(aEventTarget);
+    if (target) {
+      target->Dispatch(runnable, NS_DISPATCH_NORMAL);
+    } else {
+      runnable->Run();
+    }
+  }
+
+  NS_IMETHOD
+  Run() override {
+    mCallback->OnInputStreamReady(mStream);
+    mCallback = nullptr;
+    mStream = nullptr;
+    return NS_OK;
+  }
+
+ private:
+  InputStreamCallbackRunnable(
+      already_AddRefed<nsIInputStreamCallback> aCallback,
+      RemoteLazyInputStream* aStream)
+      : DiscardableRunnable("dom::InputStreamCallbackRunnable"),
+        mCallback(std::move(aCallback)),
+        mStream(aStream) {
+    MOZ_ASSERT(mCallback);
+    MOZ_ASSERT(mStream);
+  }
+
+  RefPtr<nsIInputStreamCallback> mCallback;
+  RefPtr<RemoteLazyInputStream> mStream;
+};
+
+class FileMetadataCallbackRunnable final : public DiscardableRunnable {
+ public:
+  static void Execute(nsIFileMetadataCallback* aCallback,
+                      nsIEventTarget* aEventTarget,
+                      RemoteLazyInputStream* aStream) {
+    MOZ_ASSERT(aCallback);
+    MOZ_ASSERT(aEventTarget);
+
+    RefPtr<FileMetadataCallbackRunnable> runnable =
+        new FileMetadataCallbackRunnable(aCallback, aStream);
+
+    nsCOMPtr<nsIEventTarget> target = aEventTarget;
+    target->Dispatch(runnable, NS_DISPATCH_NORMAL);
+  }
+
+  NS_IMETHOD
+  Run() override {
+    mCallback->OnFileMetadataReady(mStream);
+    mCallback = nullptr;
+    mStream = nullptr;
+    return NS_OK;
+  }
+
+ private:
+  FileMetadataCallbackRunnable(nsIFileMetadataCallback* aCallback,
+                               RemoteLazyInputStream* aStream)
+      : DiscardableRunnable("dom::FileMetadataCallbackRunnable"),
+        mCallback(aCallback),
+        mStream(aStream) {
+    MOZ_ASSERT(mCallback);
+    MOZ_ASSERT(mStream);
+  }
+
+  nsCOMPtr<nsIFileMetadataCallback> mCallback;
+  RefPtr<RemoteLazyInputStream> mStream;
+};
+
+}  // namespace
+
+NS_IMPL_ADDREF(RemoteLazyInputStream);
+NS_IMPL_RELEASE(RemoteLazyInputStream);
+
+NS_INTERFACE_MAP_BEGIN(RemoteLazyInputStream)
+  NS_INTERFACE_MAP_ENTRY(nsIInputStream)
+  NS_INTERFACE_MAP_ENTRY(nsIAsyncInputStream)
+  NS_INTERFACE_MAP_ENTRY(nsIInputStreamCallback)
+  NS_INTERFACE_MAP_ENTRY(nsICloneableInputStream)
+  NS_INTERFACE_MAP_ENTRY(nsICloneableInputStreamWithRange)
+  NS_INTERFACE_MAP_ENTRY(nsIIPCSerializableInputStream)
+  NS_INTERFACE_MAP_ENTRY(nsIFileMetadata)
+  NS_INTERFACE_MAP_ENTRY(nsIAsyncFileMetadata)
+  NS_INTERFACE_MAP_ENTRY(nsIInputStreamLength)
+  NS_INTERFACE_MAP_ENTRY(nsIAsyncInputStreamLength)
+  NS_INTERFACE_MAP_ENTRY(mozIRemoteLazyInputStream)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIInputStream)
+NS_INTERFACE_MAP_END
+
+RemoteLazyInputStream::RemoteLazyInputStream(RemoteLazyInputStreamChild* aActor,
+                                             uint64_t aStart, uint64_t aLength)
+    : mStart(aStart), mLength(aLength), mState(eInit), mActor(aActor) {
+  MOZ_ASSERT(aActor);
+
+  mActor->StreamCreated();
+
+  auto storage = RemoteLazyInputStreamStorage::Get().unwrapOr(nullptr);
+  if (storage) {
+    nsCOMPtr<nsIInputStream> stream;
+    storage->GetStream(mActor->StreamID(), mStart, mLength,
+                       getter_AddRefs(stream));
+    if (stream) {
+      mState = eRunning;
+      mInnerStream = stream;
+    }
+  }
+}
+
+RemoteLazyInputStream::RemoteLazyInputStream(nsIInputStream* aStream)
+    : mStart(0), mLength(UINT64_MAX), mState(eRunning), mInnerStream(aStream) {}
+
+static already_AddRefed<RemoteLazyInputStreamChild> BindChildActor(
+    nsID aId, mozilla::ipc::Endpoint<PRemoteLazyInputStreamChild> aEndpoint) {
+  auto* thread = RemoteLazyInputStreamThread::GetOrCreate();
+  if (NS_WARN_IF(!thread)) {
+    return nullptr;
+  }
+  auto actor = MakeRefPtr<RemoteLazyInputStreamChild>(aId);
+  thread->Dispatch(
+      NS_NewRunnableFunction("RemoteLazyInputStream::BindChildActor",
+                             [actor, childEp = std::move(aEndpoint)]() mutable {
+                               bool ok = childEp.Bind(actor);
+                               MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Debug,
+                                       ("Binding child actor for %s (%p): %s",
+                                        nsIDToCString(actor->StreamID()).get(),
+                                        actor.get(), ok ? "OK" : "ERROR"));
+                             }));
+
+  return actor.forget();
+}
+
+already_AddRefed<RemoteLazyInputStream> RemoteLazyInputStream::WrapStream(
+    nsIInputStream* aInputStream) {
+  MOZ_ASSERT(XRE_IsParentProcess());
+  if (nsCOMPtr<mozIRemoteLazyInputStream> lazyStream =
+          do_QueryInterface(aInputStream)) {
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Debug,
+            ("Returning already-wrapped stream"));
+    return lazyStream.forget().downcast<RemoteLazyInputStream>();
+  }
+
+  // If we have a stream and are in the parent process, create a new actor pair
+  // and transfer ownership of the stream into storage.
+  auto streamStorage = RemoteLazyInputStreamStorage::Get();
+  if (NS_WARN_IF(streamStorage.isErr())) {
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Warning,
+            ("Cannot wrap with no storage!"));
+    return nullptr;
+  }
+
+  nsID id = nsID::GenerateUUID();
+  MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+          ("Wrapping stream %p as %s", aInputStream, nsIDToCString(id).get()));
+  streamStorage.inspect()->AddStream(aInputStream, id);
+
+  mozilla::ipc::Endpoint<PRemoteLazyInputStreamParent> parentEp;
+  mozilla::ipc::Endpoint<PRemoteLazyInputStreamChild> childEp;
+  MOZ_ALWAYS_SUCCEEDS(
+      PRemoteLazyInputStream::CreateEndpoints(&parentEp, &childEp));
+
+  // Bind the actor on our background thread.
+  streamStorage.inspect()->TaskQueue()->Dispatch(NS_NewRunnableFunction(
+      "RemoteLazyInputStreamParent::Bind",
+      [parentEp = std::move(parentEp), id]() mutable {
+        auto actor = MakeRefPtr<RemoteLazyInputStreamParent>(id);
+        bool ok = parentEp.Bind(actor);
+        MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Debug,
+                ("Binding parent actor for %s (%p): %s",
+                 nsIDToCString(id).get(), actor.get(), ok ? "OK" : "ERROR"));
+      }));
+
+  RefPtr<RemoteLazyInputStreamChild> actor =
+      BindChildActor(id, std::move(childEp));
+
+  if (!actor) {
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Warning,
+            ("Wrapping stream failed as we are probably late in shutdown!"));
+    return do_AddRef(new RemoteLazyInputStream());
+  }
+
+  return do_AddRef(new RemoteLazyInputStream(actor));
+}
+
+NS_IMETHODIMP RemoteLazyInputStream::TakeInternalStream(
+    nsIInputStream** aStream) {
+  RefPtr<RemoteLazyInputStreamChild> actor;
+  {
+    MutexAutoLock lock(mMutex);
+    if (mState == eInit || mState == ePending) {
+      return NS_BASE_STREAM_WOULD_BLOCK;
+    }
+    if (mState == eClosed) {
+      return NS_BASE_STREAM_CLOSED;
+    }
+    if (mInputStreamCallback) {
+      MOZ_ASSERT_UNREACHABLE(
+          "Do not call TakeInternalStream after calling AsyncWait");
+      return NS_ERROR_UNEXPECTED;
+    }
+
+    // Take the inner stream and return it, then close ourselves.
+    if (mInnerStream) {
+      mInnerStream.forget(aStream);
+    } else if (mAsyncInnerStream) {
+      mAsyncInnerStream.forget(aStream);
+    }
+    mState = eClosed;
+    actor = mActor.forget();
+  }
+  if (actor) {
+    actor->StreamConsumed();
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP RemoteLazyInputStream::GetInternalStreamID(nsID& aID) {
+  MutexAutoLock lock(mMutex);
+  if (!mActor) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  aID = mActor->StreamID();
+  return NS_OK;
+}
+
+RemoteLazyInputStream::~RemoteLazyInputStream() { Close(); }
+
+nsCString RemoteLazyInputStream::Describe() {
+  const char* state = "?";
+  switch (mState) {
+    case eInit:
+      state = "i";
+      break;
+    case ePending:
+      state = "p";
+      break;
+    case eRunning:
+      state = "r";
+      break;
+    case eClosed:
+      state = "c";
+      break;
+  }
+  return nsPrintfCString(
+      "[%p, %s, %s, %p%s, %s%s|%s%s]", this, state,
+      mActor ? nsIDToCString(mActor->StreamID()).get() : "<no actor>",
+      mInnerStream ? mInnerStream.get() : mAsyncInnerStream.get(),
+      mAsyncInnerStream ? "(A)" : "", mInputStreamCallback ? "I" : "",
+      mInputStreamCallbackEventTarget ? "+" : "",
+      mFileMetadataCallback ? "F" : "",
+      mFileMetadataCallbackEventTarget ? "+" : "");
+}
+
+// nsIInputStream interface
+
+NS_IMETHODIMP
+RemoteLazyInputStream::Available(uint64_t* aLength) {
+  nsCOMPtr<nsIAsyncInputStream> stream;
+  {
+    MutexAutoLock lock(mMutex);
+
+    // We don't have a remoteStream yet: let's return 0.
+    if (mState == eInit || mState == ePending) {
+      *aLength = 0;
+      return NS_OK;
+    }
+
+    if (mState == eClosed) {
+      return NS_BASE_STREAM_CLOSED;
+    }
+
+    MOZ_ASSERT(mState == eRunning);
+    MOZ_ASSERT(mInnerStream || mAsyncInnerStream);
+
+    nsresult rv = EnsureAsyncRemoteStream();
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    stream = mAsyncInnerStream;
+  }
+
+  MOZ_ASSERT(stream);
+  return stream->Available(aLength);
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStream::Read(char* aBuffer, uint32_t aCount,
+                            uint32_t* aReadCount) {
+  nsCOMPtr<nsIAsyncInputStream> stream;
+  {
+    MutexAutoLock lock(mMutex);
+
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+            ("Read(%u) %s", aCount, Describe().get()));
+
+    // Read is not available is we don't have a remoteStream.
+    if (mState == eInit || mState == ePending) {
+      return NS_BASE_STREAM_WOULD_BLOCK;
+    }
+
+    if (mState == eClosed) {
+      return NS_BASE_STREAM_CLOSED;
+    }
+
+    MOZ_ASSERT(mState == eRunning);
+    MOZ_ASSERT(mInnerStream || mAsyncInnerStream);
+
+    nsresult rv = EnsureAsyncRemoteStream();
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    stream = mAsyncInnerStream;
+  }
+
+  MOZ_ASSERT(stream);
+  nsresult rv = stream->Read(aBuffer, aCount, aReadCount);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  // If some data has been read, we mark the stream as consumed.
+  if (*aReadCount > 0) {
+    MarkConsumed();
+  }
+
+  MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+          ("Read %u/%u bytes", *aReadCount, aCount));
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStream::ReadSegments(nsWriteSegmentFun aWriter, void* aClosure,
+                                    uint32_t aCount, uint32_t* aResult) {
+  nsCOMPtr<nsIAsyncInputStream> stream;
+  {
+    MutexAutoLock lock(mMutex);
+
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+            ("ReadSegments(%u) %s", aCount, Describe().get()));
+
+    // ReadSegments is not available is we don't have a remoteStream.
+    if (mState == eInit || mState == ePending) {
+      return NS_BASE_STREAM_WOULD_BLOCK;
+    }
+
+    if (mState == eClosed) {
+      return NS_BASE_STREAM_CLOSED;
+    }
+
+    MOZ_ASSERT(mState == eRunning);
+    MOZ_ASSERT(mInnerStream || mAsyncInnerStream);
+
+    nsresult rv = EnsureAsyncRemoteStream();
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Warning,
+              ("EnsureAsyncRemoteStream failed! %s %s",
+               mozilla::GetStaticErrorName(rv), Describe().get()));
+      return rv;
+    }
+
+    stream = mAsyncInnerStream;
+  }
+
+  MOZ_ASSERT(stream);
+  nsresult rv = stream->ReadSegments(aWriter, aClosure, aCount, aResult);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  // If some data has been read, we mark the stream as consumed.
+  if (*aResult != 0) {
+    MarkConsumed();
+  }
+
+  MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+          ("ReadSegments %u/%u bytes", *aResult, aCount));
+
+  return NS_OK;
+}
+
+void RemoteLazyInputStream::MarkConsumed() {
+  RefPtr<RemoteLazyInputStreamChild> actor;
+  {
+    MutexAutoLock lock(mMutex);
+    if (mActor) {
+      MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Debug,
+              ("MarkConsumed %s", Describe().get()));
+    }
+
+    actor = mActor.forget();
+  }
+  if (actor) {
+    actor->StreamConsumed();
+  }
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStream::IsNonBlocking(bool* aNonBlocking) {
+  *aNonBlocking = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStream::Close() {
+  RefPtr<RemoteLazyInputStreamChild> actor;
+
+  nsCOMPtr<nsIAsyncInputStream> asyncInnerStream;
+  nsCOMPtr<nsIInputStream> innerStream;
+
+  RefPtr<nsIInputStreamCallback> inputStreamCallback;
+  nsCOMPtr<nsIEventTarget> inputStreamCallbackEventTarget;
+
+  {
+    MutexAutoLock lock(mMutex);
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Debug,
+            ("Close %s", Describe().get()));
+
+    actor = mActor.forget();
+
+    asyncInnerStream = mAsyncInnerStream.forget();
+    innerStream = mInnerStream.forget();
+
+    // TODO(Bug 1737783): Notify to the mFileMetadataCallback that this
+    // lazy input stream has been closed.
+    mFileMetadataCallback = nullptr;
+    mFileMetadataCallbackEventTarget = nullptr;
+
+    inputStreamCallback = mInputStreamCallback.forget();
+    inputStreamCallbackEventTarget = mInputStreamCallbackEventTarget.forget();
+
+    mState = eClosed;
+  }
+
+  if (actor) {
+    actor->StreamConsumed();
+  }
+
+  if (inputStreamCallback) {
+    InputStreamCallbackRunnable::Execute(
+        inputStreamCallback.forget(), inputStreamCallbackEventTarget.forget(),
+        this);
+  }
+
+  if (asyncInnerStream) {
+    asyncInnerStream->CloseWithStatus(NS_BASE_STREAM_CLOSED);
+  }
+
+  if (innerStream) {
+    innerStream->Close();
+  }
+
+  return NS_OK;
+}
+
+// nsICloneableInputStream interface
+
+NS_IMETHODIMP
+RemoteLazyInputStream::GetCloneable(bool* aCloneable) {
+  *aCloneable = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStream::Clone(nsIInputStream** aResult) {
+  return CloneWithRange(0, UINT64_MAX, aResult);
+}
+
+// nsICloneableInputStreamWithRange interface
+
+NS_IMETHODIMP
+RemoteLazyInputStream::CloneWithRange(uint64_t aStart, uint64_t aLength,
+                                      nsIInputStream** aResult) {
+  MutexAutoLock lock(mMutex);
+  MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Debug,
+          ("CloneWithRange %" PRIu64 " %" PRIu64 " %s", aStart, aLength,
+           Describe().get()));
+
+  nsresult rv;
+
+  RefPtr<RemoteLazyInputStream> stream;
+  if (mState == eClosed) {
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose, ("Cloning closed stream"));
+    stream = new RemoteLazyInputStream();
+    stream.forget(aResult);
+    return NS_OK;
+  }
+
+  uint64_t start = 0;
+  uint64_t length = 0;
+  auto maxLength = CheckedUint64(mLength) - aStart;
+  if (maxLength.isValid()) {
+    start = mStart + aStart;
+    length = std::min(maxLength.value(), aLength);
+  }
+
+  // If the slice would be empty, wrap an empty input stream and return it.
+  if (length == 0) {
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose, ("Creating empty stream"));
+
+    nsCOMPtr<nsIInputStream> emptyStream;
+    rv = NS_NewCStringInputStream(getter_AddRefs(emptyStream), ""_ns);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    stream = new RemoteLazyInputStream(emptyStream);
+    stream.forget(aResult);
+    return NS_OK;
+  }
+
+  // If we still have a connection to our actor, that means we haven't read any
+  // data yet, and can clone + slice by building a new stream backed by the same
+  // actor.
+  if (mActor) {
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+            ("Cloning stream with actor"));
+
+    stream = new RemoteLazyInputStream(mActor, start, length);
+    stream.forget(aResult);
+    return NS_OK;
+  }
+
+  // We no longer have our actor, either because we were constructed without
+  // one, or we've already begun reading. Perform the clone locally on our inner
+  // input stream.
+
+  nsCOMPtr<nsIInputStream> innerStream = mInnerStream;
+  if (mAsyncInnerStream) {
+    innerStream = mAsyncInnerStream;
+  }
+
+  nsCOMPtr<nsICloneableInputStream> cloneable = do_QueryInterface(innerStream);
+  if (!cloneable || !cloneable->GetCloneable()) {
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+            ("Cloning non-cloneable stream - copying to pipe"));
+
+    // If our internal stream isn't cloneable, to perform a clone we'll need to
+    // copy into a pipe and replace our internal stream.
+    nsCOMPtr<nsIAsyncInputStream> pipeIn;
+    nsCOMPtr<nsIAsyncOutputStream> pipeOut;
+    NS_NewPipe2(getter_AddRefs(pipeIn), getter_AddRefs(pipeOut), true, true);
+
+    RefPtr<RemoteLazyInputStreamThread> thread =
+        RemoteLazyInputStreamThread::GetOrCreate();
+    if (NS_WARN_IF(!thread)) {
+      return NS_ERROR_ILLEGAL_DURING_SHUTDOWN;
+    }
+
+    mAsyncInnerStream = pipeIn;
+    mInnerStream = nullptr;
+
+    // If we have a callback pending, we need to re-call AsyncWait on the inner
+    // stream. This should not re-enter us immediately, as `pipeIn` hasn't been
+    // sent any data yet, but we may be called again as soon as `NS_AsyncCopy`
+    // has begun copying.
+    if (mInputStreamCallback) {
+      mAsyncInnerStream->AsyncWait(this, mInputStreamCallbackFlags,
+                                   mInputStreamCallbackRequestedCount,
+                                   mInputStreamCallbackEventTarget);
+    }
+
+    rv = NS_AsyncCopy(innerStream, pipeOut, thread,
+                      NS_ASYNCCOPY_VIA_WRITESEGMENTS);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      // The copy failed, revert the changes we did and restore our previous
+      // inner stream.
+      mAsyncInnerStream = nullptr;
+      mInnerStream = innerStream;
+      return rv;
+    }
+
+    cloneable = do_QueryInterface(mAsyncInnerStream);
+  }
+
+  MOZ_ASSERT(cloneable && cloneable->GetCloneable());
+
+  // Check if we can clone more efficiently with a range.
+  if (length < UINT64_MAX) {
+    if (nsCOMPtr<nsICloneableInputStreamWithRange> cloneableWithRange =
+            do_QueryInterface(cloneable)) {
+      MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose, ("Cloning with range"));
+      nsCOMPtr<nsIInputStream> cloned;
+      rv = cloneableWithRange->CloneWithRange(start, length,
+                                              getter_AddRefs(cloned));
+      if (NS_FAILED(rv)) {
+        return rv;
+      }
+
+      stream = new RemoteLazyInputStream(cloned);
+      stream.forget(aResult);
+      return NS_OK;
+    }
+  }
+
+  // Directly clone our inner stream, and then slice it if needed.
+  nsCOMPtr<nsIInputStream> cloned;
+  rv = cloneable->Clone(getter_AddRefs(cloned));
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  if (length < UINT64_MAX) {
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+            ("Slicing stream with %" PRIu64 " %" PRIu64, start, length));
+    cloned = new SlicedInputStream(cloned.forget(), start, length);
+  }
+
+  stream = new RemoteLazyInputStream(cloned);
+  stream.forget(aResult);
+  return NS_OK;
+}
+
+// nsIAsyncInputStream interface
+
+NS_IMETHODIMP
+RemoteLazyInputStream::CloseWithStatus(nsresult aStatus) { return Close(); }
+
+NS_IMETHODIMP
+RemoteLazyInputStream::AsyncWait(nsIInputStreamCallback* aCallback,
+                                 uint32_t aFlags, uint32_t aRequestedCount,
+                                 nsIEventTarget* aEventTarget) {
+  // Ensure we always have an event target for AsyncWait callbacks, so that
+  // calls to `AsyncWait` cannot reenter us with `OnInputStreamReady`.
+  nsCOMPtr<nsIEventTarget> eventTarget = aEventTarget;
+  if (aCallback && !eventTarget) {
+    eventTarget = RemoteLazyInputStreamThread::GetOrCreate();
+    if (NS_WARN_IF(!eventTarget)) {
+      return NS_ERROR_ILLEGAL_DURING_SHUTDOWN;
+    }
+  }
+
+  {
+    MutexAutoLock lock(mMutex);
+
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+            ("AsyncWait(%p, %u, %u, %p) %s", aCallback, aFlags, aRequestedCount,
+             aEventTarget, Describe().get()));
+
+    // See RemoteLazyInputStream.h for more information about this state
+    // machine.
+
+    nsCOMPtr<nsIAsyncInputStream> stream;
+    switch (mState) {
+      // First call, we need to retrieve the stream from the parent actor.
+      case eInit:
+        MOZ_ASSERT(mActor);
+
+        mInputStreamCallback = aCallback;
+        mInputStreamCallbackEventTarget = eventTarget;
+        mInputStreamCallbackFlags = aFlags;
+        mInputStreamCallbackRequestedCount = aRequestedCount;
+        mState = ePending;
+
+        StreamNeeded();
+        return NS_OK;
+
+      // We are still waiting for the remote inputStream
+      case ePending: {
+        if (NS_WARN_IF(mInputStreamCallback && aCallback &&
+                       mInputStreamCallback != aCallback)) {
+          return NS_ERROR_FAILURE;
+        }
+
+        mInputStreamCallback = aCallback;
+        mInputStreamCallbackEventTarget = eventTarget;
+        mInputStreamCallbackFlags = aFlags;
+        mInputStreamCallbackRequestedCount = aRequestedCount;
+        return NS_OK;
+      }
+
+      // We have the remote inputStream, let's check if we can execute the
+      // callback.
+      case eRunning: {
+        if (NS_WARN_IF(mInputStreamCallback && aCallback &&
+                       mInputStreamCallback != aCallback)) {
+          return NS_ERROR_FAILURE;
+        }
+
+        nsresult rv = EnsureAsyncRemoteStream();
+        if (NS_WARN_IF(NS_FAILED(rv))) {
+          return rv;
+        }
+
+        mInputStreamCallback = aCallback;
+        mInputStreamCallbackEventTarget = eventTarget;
+        mInputStreamCallbackFlags = aFlags;
+        mInputStreamCallbackRequestedCount = aRequestedCount;
+
+        stream = mAsyncInnerStream;
+        break;
+      }
+
+      case eClosed:
+        [[fallthrough]];
+      default:
+        MOZ_ASSERT(mState == eClosed);
+        if (NS_WARN_IF(mInputStreamCallback && aCallback &&
+                       mInputStreamCallback != aCallback)) {
+          return NS_ERROR_FAILURE;
+        }
+        break;
+    }
+
+    if (stream) {
+      return stream->AsyncWait(aCallback ? this : nullptr, aFlags,
+                               aRequestedCount, eventTarget);
+    }
+  }
+
+  if (aCallback) {
+    // if stream is nullptr here, that probably means the stream has
+    // been closed and the callback can be executed immediately
+    InputStreamCallbackRunnable::Execute(do_AddRef(aCallback),
+                                         do_AddRef(eventTarget), this);
+  }
+  return NS_OK;
+}
+
+void RemoteLazyInputStream::StreamNeeded() {
+  MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Debug,
+          ("StreamNeeded %s", Describe().get()));
+
+  auto* thread = RemoteLazyInputStreamThread::GetOrCreate();
+  if (NS_WARN_IF(!thread)) {
+    return;
+  }
+  thread->Dispatch(NS_NewRunnableFunction(
+      "RemoteLazyInputStream::StreamNeeded",
+      [self = RefPtr{this}, actor = mActor, start = mStart, length = mLength] {
+        MOZ_LOG(
+            gRemoteLazyStreamLog, LogLevel::Debug,
+            ("Sending StreamNeeded(%" PRIu64 " %" PRIu64 ") %s %d", start,
+             length, nsIDToCString(actor->StreamID()).get(), actor->CanSend()));
+
+        actor->SendStreamNeeded(
+            start, length,
+            [self](const Maybe<mozilla::ipc::IPCStream>& aStream) {
+              // Try to deserialize the stream from our remote, and close our
+              // stream if it fails.
+              nsCOMPtr<nsIInputStream> stream =
+                  mozilla::ipc::DeserializeIPCStream(aStream);
+              if (NS_WARN_IF(!stream)) {
+                NS_WARNING("Failed to deserialize IPC stream");
+                self->Close();
+              }
+
+              // Lock our mutex to update the inner stream, and collect any
+              // callbacks which we need to invoke.
+              MutexAutoLock lock(self->mMutex);
+
+              MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Debug,
+                      ("ResolveStreamNeeded(%p) %s", stream.get(),
+                       self->Describe().get()));
+
+              if (self->mState == ePending) {
+                self->mInnerStream = stream.forget();
+                self->mState = eRunning;
+
+                // Notify any listeners that we've now acquired the underlying
+                // stream, so file metadata information will be available.
+                nsCOMPtr<nsIFileMetadataCallback> fileMetadataCallback =
+                    self->mFileMetadataCallback.forget();
+                nsCOMPtr<nsIEventTarget> fileMetadataCallbackEventTarget =
+                    self->mFileMetadataCallbackEventTarget.forget();
+                if (fileMetadataCallback) {
+                  FileMetadataCallbackRunnable::Execute(
+                      fileMetadataCallback, fileMetadataCallbackEventTarget,
+                      self);
+                }
+
+                // **NOTE** we can re-enter this class here **NOTE**
+                // If we already have an input stream callback, attempt to
+                // register ourselves with AsyncWait on the underlying stream.
+                if (self->mInputStreamCallback) {
+                  if (NS_FAILED(self->EnsureAsyncRemoteStream()) ||
+                      NS_FAILED(self->mAsyncInnerStream->AsyncWait(
+                          self, self->mInputStreamCallbackFlags,
+                          self->mInputStreamCallbackRequestedCount,
+                          self->mInputStreamCallbackEventTarget))) {
+                    InputStreamCallbackRunnable::Execute(
+                        self->mInputStreamCallback.forget(),
+                        self->mInputStreamCallbackEventTarget.forget(), self);
+                  }
+                }
+              }
+
+              if (stream) {
+                NS_WARNING("Failed to save stream, closing it");
+                stream->Close();
+              }
+            },
+            [self](mozilla::ipc::ResponseRejectReason) {
+              NS_WARNING("SendStreamNeeded rejected");
+              self->Close();
+            });
+      }));
+}
+
+// nsIInputStreamCallback
+
+NS_IMETHODIMP
+RemoteLazyInputStream::OnInputStreamReady(nsIAsyncInputStream* aStream) {
+  RefPtr<nsIInputStreamCallback> callback;
+  nsCOMPtr<nsIEventTarget> callbackEventTarget;
+  {
+    MutexAutoLock lock(mMutex);
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Debug,
+            ("OnInputStreamReady %s", Describe().get()));
+
+    // We have been closed in the meantime.
+    if (mState == eClosed) {
+      return NS_OK;
+    }
+
+    // We got a callback from the wrong stream, likely due to a `CloneWithRange`
+    // call while we were waiting. Ignore this callback.
+    if (mAsyncInnerStream != aStream) {
+      return NS_OK;
+    }
+
+    MOZ_ASSERT(mState == eRunning);
+
+    // The callback has been canceled in the meantime.
+    if (!mInputStreamCallback) {
+      return NS_OK;
+    }
+
+    callback.swap(mInputStreamCallback);
+    callbackEventTarget.swap(mInputStreamCallbackEventTarget);
+  }
+
+  // This must be the last operation because the execution of the callback can
+  // be synchronous.
+  MOZ_ASSERT(callback);
+  InputStreamCallbackRunnable::Execute(callback.forget(),
+                                       callbackEventTarget.forget(), this);
+  return NS_OK;
+}
+
+// nsIIPCSerializableInputStream
+
+void RemoteLazyInputStream::SerializedComplexity(uint32_t aMaxSize,
+                                                 uint32_t* aSizeUsed,
+                                                 uint32_t* aNewPipes,
+                                                 uint32_t* aTransferables) {
+  *aTransferables = 1;
+}
+
+void RemoteLazyInputStream::Serialize(mozilla::ipc::InputStreamParams& aParams,
+                                      uint32_t aMaxSize, uint32_t* aSizeUsed) {
+  *aSizeUsed = 0;
+  aParams = mozilla::ipc::RemoteLazyInputStreamParams(this);
+}
+
+bool RemoteLazyInputStream::Deserialize(
+    const mozilla::ipc::InputStreamParams& aParams) {
+  MOZ_CRASH("This should never be called.");
+  return false;
+}
+
+// nsIAsyncFileMetadata
+
+NS_IMETHODIMP
+RemoteLazyInputStream::AsyncFileMetadataWait(nsIFileMetadataCallback* aCallback,
+                                             nsIEventTarget* aEventTarget) {
+  MOZ_ASSERT(!!aCallback == !!aEventTarget);
+
+  // If we have the callback, we must have the event target.
+  if (NS_WARN_IF(!!aCallback != !!aEventTarget)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // See RemoteLazyInputStream.h for more information about this state
+  // machine.
+
+  {
+    MutexAutoLock lock(mMutex);
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Debug,
+            ("AsyncFileMetadataWait(%p, %p) %s", aCallback, aEventTarget,
+             Describe().get()));
+
+    switch (mState) {
+      // First call, we need to retrieve the stream from the parent actor.
+      case eInit:
+        MOZ_ASSERT(mActor);
+
+        mFileMetadataCallback = aCallback;
+        mFileMetadataCallbackEventTarget = aEventTarget;
+        mState = ePending;
+
+        StreamNeeded();
+        return NS_OK;
+
+      // We are still waiting for the remote inputStream
+      case ePending:
+        if (mFileMetadataCallback && aCallback) {
+          return NS_ERROR_FAILURE;
+        }
+
+        mFileMetadataCallback = aCallback;
+        mFileMetadataCallbackEventTarget = aEventTarget;
+        return NS_OK;
+
+      // We have the remote inputStream, let's check if we can execute the
+      // callback.
+      case eRunning:
+        break;
+
+      // Stream is closed.
+      default:
+        MOZ_ASSERT(mState == eClosed);
+        return NS_BASE_STREAM_CLOSED;
+    }
+
+    MOZ_ASSERT(mState == eRunning);
+  }
+
+  FileMetadataCallbackRunnable::Execute(aCallback, aEventTarget, this);
+  return NS_OK;
+}
+
+// nsIFileMetadata
+
+NS_IMETHODIMP
+RemoteLazyInputStream::GetSize(int64_t* aRetval) {
+  nsCOMPtr<nsIFileMetadata> fileMetadata;
+  {
+    MutexAutoLock lock(mMutex);
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+            ("GetSize %s", Describe().get()));
+
+    fileMetadata = do_QueryInterface(mInnerStream);
+    if (!fileMetadata) {
+      return mState == eClosed ? NS_BASE_STREAM_CLOSED : NS_ERROR_FAILURE;
+    }
+  }
+
+  return fileMetadata->GetSize(aRetval);
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStream::GetLastModified(int64_t* aRetval) {
+  nsCOMPtr<nsIFileMetadata> fileMetadata;
+  {
+    MutexAutoLock lock(mMutex);
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+            ("GetLastModified %s", Describe().get()));
+
+    fileMetadata = do_QueryInterface(mInnerStream);
+    if (!fileMetadata) {
+      return mState == eClosed ? NS_BASE_STREAM_CLOSED : NS_ERROR_FAILURE;
+    }
+  }
+
+  return fileMetadata->GetLastModified(aRetval);
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStream::GetFileDescriptor(PRFileDesc** aRetval) {
+  nsCOMPtr<nsIFileMetadata> fileMetadata;
+  {
+    MutexAutoLock lock(mMutex);
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+            ("GetFileDescriptor %s", Describe().get()));
+
+    fileMetadata = do_QueryInterface(mInnerStream);
+    if (!fileMetadata) {
+      return mState == eClosed ? NS_BASE_STREAM_CLOSED : NS_ERROR_FAILURE;
+    }
+  }
+
+  return fileMetadata->GetFileDescriptor(aRetval);
+}
+
+nsresult RemoteLazyInputStream::EnsureAsyncRemoteStream() {
+  // We already have an async remote stream.
+  if (mAsyncInnerStream) {
+    return NS_OK;
+  }
+
+  MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Debug,
+          ("EnsureAsyncRemoteStream %s", Describe().get()));
+
+  if (NS_WARN_IF(!mInnerStream)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsCOMPtr<nsIInputStream> stream = mInnerStream;
+
+  // Check if the stream is blocking, if it is, we want to make it non-blocking
+  // using a pipe.
+  bool nonBlocking = false;
+  nsresult rv = stream->IsNonBlocking(&nonBlocking);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  // We don't return NS_ERROR_NOT_IMPLEMENTED from ReadSegments,
+  // so it's possible that callers are expecting us to succeed in the future.
+  // We need to make sure the stream we return here supports ReadSegments,
+  // so wrap if in a buffered stream if necessary.
+  //
+  // We only need to do this if we won't be wrapping the stream in a pipe, which
+  // will add buffering anyway.
+  if (nonBlocking && !NS_InputStreamIsBuffered(stream)) {
+    nsCOMPtr<nsIInputStream> bufferedStream;
+    nsresult rv = NS_NewBufferedInputStream(getter_AddRefs(bufferedStream),
+                                            stream.forget(), 4096);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    stream = bufferedStream;
+  }
+
+  nsCOMPtr<nsIAsyncInputStream> asyncStream = do_QueryInterface(stream);
+
+  // If non-blocking and non-async, let's use NonBlockingAsyncInputStream.
+  if (nonBlocking && !asyncStream) {
+    rv = NonBlockingAsyncInputStream::Create(stream.forget(),
+                                             getter_AddRefs(asyncStream));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    MOZ_ASSERT(asyncStream);
+  }
+
+  if (!asyncStream) {
+    // Let's make the stream async using the DOMFile thread.
+    nsCOMPtr<nsIAsyncInputStream> pipeIn;
+    nsCOMPtr<nsIAsyncOutputStream> pipeOut;
+    NS_NewPipe2(getter_AddRefs(pipeIn), getter_AddRefs(pipeOut), true, true);
+
+    RefPtr<RemoteLazyInputStreamThread> thread =
+        RemoteLazyInputStreamThread::GetOrCreate();
+    if (NS_WARN_IF(!thread)) {
+      return NS_ERROR_ILLEGAL_DURING_SHUTDOWN;
+    }
+
+    rv = NS_AsyncCopy(stream, pipeOut, thread, NS_ASYNCCOPY_VIA_WRITESEGMENTS);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    asyncStream = pipeIn;
+  }
+
+  MOZ_ASSERT(asyncStream);
+  mAsyncInnerStream = asyncStream;
+  mInnerStream = nullptr;
+
+  return NS_OK;
+}
+
+// nsIInputStreamLength
+
+NS_IMETHODIMP
+RemoteLazyInputStream::Length(int64_t* aLength) {
+  MutexAutoLock lock(mMutex);
+
+  if (mState == eClosed) {
+    return NS_BASE_STREAM_CLOSED;
+  }
+
+  if (!mActor) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  return NS_BASE_STREAM_WOULD_BLOCK;
+}
+
+namespace {
+
+class InputStreamLengthCallbackRunnable final : public DiscardableRunnable {
+ public:
+  static void Execute(nsIInputStreamLengthCallback* aCallback,
+                      nsIEventTarget* aEventTarget,
+                      RemoteLazyInputStream* aStream, int64_t aLength) {
+    MOZ_ASSERT(aCallback);
+    MOZ_ASSERT(aEventTarget);
+
+    RefPtr<InputStreamLengthCallbackRunnable> runnable =
+        new InputStreamLengthCallbackRunnable(aCallback, aStream, aLength);
+
+    nsCOMPtr<nsIEventTarget> target = aEventTarget;
+    target->Dispatch(runnable, NS_DISPATCH_NORMAL);
+  }
+
+  NS_IMETHOD
+  Run() override {
+    mCallback->OnInputStreamLengthReady(mStream, mLength);
+    mCallback = nullptr;
+    mStream = nullptr;
+    return NS_OK;
+  }
+
+ private:
+  InputStreamLengthCallbackRunnable(nsIInputStreamLengthCallback* aCallback,
+                                    RemoteLazyInputStream* aStream,
+                                    int64_t aLength)
+      : DiscardableRunnable("dom::InputStreamLengthCallbackRunnable"),
+        mCallback(aCallback),
+        mStream(aStream),
+        mLength(aLength) {
+    MOZ_ASSERT(mCallback);
+    MOZ_ASSERT(mStream);
+  }
+
+  nsCOMPtr<nsIInputStreamLengthCallback> mCallback;
+  RefPtr<RemoteLazyInputStream> mStream;
+  const int64_t mLength;
+};
+
+}  // namespace
+
+// nsIAsyncInputStreamLength
+
+NS_IMETHODIMP
+RemoteLazyInputStream::AsyncLengthWait(nsIInputStreamLengthCallback* aCallback,
+                                       nsIEventTarget* aEventTarget) {
+  // If we have the callback, we must have the event target.
+  if (NS_WARN_IF(!!aCallback != !!aEventTarget)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  {
+    MutexAutoLock lock(mMutex);
+
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+            ("AsyncLengthWait(%p, %p) %s", aCallback, aEventTarget,
+             Describe().get()));
+
+    if (mActor) {
+      if (aCallback) {
+        auto* thread = RemoteLazyInputStreamThread::GetOrCreate();
+        if (NS_WARN_IF(!thread)) {
+          return NS_ERROR_ILLEGAL_DURING_SHUTDOWN;
+        }
+        thread->Dispatch(NS_NewRunnableFunction(
+            "RemoteLazyInputStream::AsyncLengthWait",
+            [self = RefPtr{this}, actor = mActor,
+             callback = nsCOMPtr{aCallback},
+             eventTarget = nsCOMPtr{aEventTarget}] {
+              actor->SendLengthNeeded(
+                  [self, callback, eventTarget](int64_t aLength) {
+                    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+                            ("AsyncLengthWait resolve %" PRId64, aLength));
+                    int64_t length = -1;
+                    if (aLength > 0) {
+                      uint64_t sourceLength =
+                          aLength - std::min<uint64_t>(aLength, self->mStart);
+                      length = int64_t(
+                          std::min<uint64_t>(sourceLength, self->mLength));
+                    }
+                    InputStreamLengthCallbackRunnable::Execute(
+                        callback, eventTarget, self, length);
+                  },
+                  [self, callback,
+                   eventTarget](mozilla::ipc::ResponseRejectReason) {
+                    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Warning,
+                            ("AsyncLengthWait reject"));
+                    InputStreamLengthCallbackRunnable::Execute(
+                        callback, eventTarget, self, -1);
+                  });
+            }));
+      }
+
+      return NS_OK;
+    }
+  }
+
+  MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+          ("AsyncLengthWait immediate"));
+
+  // If execution has reached here, it means the stream is either closed or
+  // consumed, and therefore the callback can be executed immediately
+  InputStreamLengthCallbackRunnable::Execute(aCallback, aEventTarget, this, -1);
+  return NS_OK;
+}
+
+void RemoteLazyInputStream::IPCWrite(IPC::MessageWriter* aWriter) {
+  // If we have an actor still, serialize efficiently by cloning our actor to
+  // maintain a reference to the parent side.
+  RefPtr<RemoteLazyInputStreamChild> actor;
+
+  nsCOMPtr<nsIInputStream> innerStream;
+
+  RefPtr<nsIInputStreamCallback> inputStreamCallback;
+  nsCOMPtr<nsIEventTarget> inputStreamCallbackEventTarget;
+
+  {
+    MutexAutoLock lock(mMutex);
+
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+            ("Serialize %s", Describe().get()));
+
+    actor = mActor.forget();
+
+    if (mAsyncInnerStream) {
+      MOZ_ASSERT(!mInnerStream);
+      innerStream = mAsyncInnerStream.forget();
+    } else {
+      innerStream = mInnerStream.forget();
+    }
+
+    // TODO(Bug 1737783): Notify to the mFileMetadataCallback that this
+    // lazy input stream has been closed.
+    mFileMetadataCallback = nullptr;
+    mFileMetadataCallbackEventTarget = nullptr;
+
+    inputStreamCallback = mInputStreamCallback.forget();
+    inputStreamCallbackEventTarget = mInputStreamCallbackEventTarget.forget();
+
+    mState = eClosed;
+  }
+
+  if (inputStreamCallback) {
+    InputStreamCallbackRunnable::Execute(
+        inputStreamCallback.forget(), inputStreamCallbackEventTarget.forget(),
+        this);
+  }
+
+  bool closed = !actor && !innerStream;
+  IPC::WriteParam(aWriter, closed);
+  if (closed) {
+    return;
+  }
+
+  // If we still have a connection to our remote actor, create a clone endpoint
+  // for it and tell it that the stream has been consumed. The clone of the
+  // connection can be transferred to another process.
+  if (actor) {
+    MOZ_LOG(
+        gRemoteLazyStreamLog, LogLevel::Debug,
+        ("Serializing as actor: %s", nsIDToCString(actor->StreamID()).get()));
+    // Create a clone of the actor, and then tell it that this stream is no
+    // longer referencing it.
+    mozilla::ipc::Endpoint<PRemoteLazyInputStreamParent> parentEp;
+    mozilla::ipc::Endpoint<PRemoteLazyInputStreamChild> childEp;
+    MOZ_ALWAYS_SUCCEEDS(
+        PRemoteLazyInputStream::CreateEndpoints(&parentEp, &childEp));
+
+    auto* thread = RemoteLazyInputStreamThread::GetOrCreate();
+    if (thread) {
+      thread->Dispatch(NS_NewRunnableFunction(
+          "RemoteLazyInputStreamChild::SendClone",
+          [actor, parentEp = std::move(parentEp)]() mutable {
+            bool ok = actor->SendClone(std::move(parentEp));
+            MOZ_LOG(
+                gRemoteLazyStreamLog, LogLevel::Verbose,
+                ("SendClone for %s: %s", nsIDToCString(actor->StreamID()).get(),
+                 ok ? "OK" : "ERR"));
+          }));
+
+    }  // else we are shutting down xpcom threads.
+
+    // NOTE: Call `StreamConsumed` after dispatching the `SendClone` runnable,
+    // as this method may dispatch a runnable to `RemoteLazyInputStreamThread`
+    // to call `SendGoodbye`, which needs to happen after `SendClone`.
+    actor->StreamConsumed();
+
+    IPC::WriteParam(aWriter, actor->StreamID());
+    IPC::WriteParam(aWriter, mStart);
+    IPC::WriteParam(aWriter, mLength);
+    IPC::WriteParam(aWriter, std::move(childEp));
+
+    if (innerStream) {
+      innerStream->Close();
+    }
+    return;
+  }
+
+  // If we have a stream and are in the parent process, create a new actor pair
+  // and transfer ownership of the stream into storage.
+  auto streamStorage = RemoteLazyInputStreamStorage::Get();
+  if (streamStorage.isOk()) {
+    MOZ_ASSERT(XRE_IsParentProcess());
+    nsID id = nsID::GenerateUUID();
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Debug,
+            ("Serializing as new stream: %s", nsIDToCString(id).get()));
+
+    streamStorage.inspect()->AddStream(innerStream, id);
+
+    mozilla::ipc::Endpoint<PRemoteLazyInputStreamParent> parentEp;
+    mozilla::ipc::Endpoint<PRemoteLazyInputStreamChild> childEp;
+    MOZ_ALWAYS_SUCCEEDS(
+        PRemoteLazyInputStream::CreateEndpoints(&parentEp, &childEp));
+
+    // Bind the actor on our background thread.
+    streamStorage.inspect()->TaskQueue()->Dispatch(NS_NewRunnableFunction(
+        "RemoteLazyInputStreamParent::Bind",
+        [parentEp = std::move(parentEp), id]() mutable {
+          auto stream = MakeRefPtr<RemoteLazyInputStreamParent>(id);
+          parentEp.Bind(stream);
+        }));
+
+    IPC::WriteParam(aWriter, id);
+    IPC::WriteParam(aWriter, 0);
+    IPC::WriteParam(aWriter, UINT64_MAX);
+    IPC::WriteParam(aWriter, std::move(childEp));
+    return;
+  }
+
+  MOZ_CRASH("Cannot serialize new RemoteLazyInputStream from this process");
+}
+
+already_AddRefed<RemoteLazyInputStream> RemoteLazyInputStream::IPCRead(
+    IPC::MessageReader* aReader) {
+  MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose, ("Deserialize"));
+
+  bool closed;
+  if (NS_WARN_IF(!IPC::ReadParam(aReader, &closed))) {
+    return nullptr;
+  }
+  if (closed) {
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+            ("Deserialize closed stream"));
+    return do_AddRef(new RemoteLazyInputStream());
+  }
+
+  nsID id{};
+  uint64_t start;
+  uint64_t length;
+  mozilla::ipc::Endpoint<PRemoteLazyInputStreamChild> endpoint;
+  if (NS_WARN_IF(!IPC::ReadParam(aReader, &id)) ||
+      NS_WARN_IF(!IPC::ReadParam(aReader, &start)) ||
+      NS_WARN_IF(!IPC::ReadParam(aReader, &length)) ||
+      NS_WARN_IF(!IPC::ReadParam(aReader, &endpoint))) {
+    return nullptr;
+  }
+
+  if (!endpoint.IsValid()) {
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Warning,
+            ("Deserialize failed due to invalid endpoint!"));
+    return do_AddRef(new RemoteLazyInputStream());
+  }
+
+  RefPtr<RemoteLazyInputStreamChild> actor =
+      BindChildActor(id, std::move(endpoint));
+
+  if (!actor) {
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Warning,
+            ("Deserialize failed as we are probably late in shutdown!"));
+    return do_AddRef(new RemoteLazyInputStream());
+  }
+
+  return do_AddRef(new RemoteLazyInputStream(actor, start, length));
+}
+
+}  // namespace mozilla
+
+void IPC::ParamTraits<mozilla::RemoteLazyInputStream*>::Write(
+    IPC::MessageWriter* aWriter, mozilla::RemoteLazyInputStream* aParam) {
+  bool nonNull = !!aParam;
+  IPC::WriteParam(aWriter, nonNull);
+  if (aParam) {
+    aParam->IPCWrite(aWriter);
+  }
+}
+
+bool IPC::ParamTraits<mozilla::RemoteLazyInputStream*>::Read(
+    IPC::MessageReader* aReader,
+    RefPtr<mozilla::RemoteLazyInputStream>* aResult) {
+  bool nonNull = false;
+  if (!IPC::ReadParam(aReader, &nonNull)) {
+    return false;
+  }
+  if (!nonNull) {
+    *aResult = nullptr;
+    return true;
+  }
+  *aResult = mozilla::RemoteLazyInputStream::IPCRead(aReader);
+  return *aResult;
+}
diff --git a/dom/file/ipc/RemoteLazyInputStream.h b/dom/file/ipc/RemoteLazyInputStream.h
new file mode 100644
index 0000000000..08bb168e27
--- /dev/null
+++ b/dom/file/ipc/RemoteLazyInputStream.h
@@ -0,0 +1,155 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_RemoteLazyInputStream_h
+#define mozilla_RemoteLazyInputStream_h
+
+#include "chrome/common/ipc_message_utils.h"
+#include "mozilla/Mutex.h"
+#include "mozIRemoteLazyInputStream.h"
+#include "nsIAsyncInputStream.h"
+#include "nsICloneableInputStream.h"
+#include "nsIFileStreams.h"
+#include "nsIIPCSerializableInputStream.h"
+#include "nsIInputStreamLength.h"
+#include "nsCOMPtr.h"
+
+namespace mozilla {
+
+class RemoteLazyInputStreamChild;
+
+class RemoteLazyInputStream final : public nsIAsyncInputStream,
+                                    public nsIInputStreamCallback,
+                                    public nsICloneableInputStreamWithRange,
+                                    public nsIIPCSerializableInputStream,
+                                    public nsIAsyncFileMetadata,
+                                    public nsIInputStreamLength,
+                                    public nsIAsyncInputStreamLength,
+                                    public mozIRemoteLazyInputStream {
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIINPUTSTREAM
+  NS_DECL_NSIASYNCINPUTSTREAM
+  NS_DECL_NSIINPUTSTREAMCALLBACK
+  NS_DECL_NSICLONEABLEINPUTSTREAM
+  NS_DECL_NSICLONEABLEINPUTSTREAMWITHRANGE
+  NS_DECL_NSIIPCSERIALIZABLEINPUTSTREAM
+  NS_DECL_NSIFILEMETADATA
+  NS_DECL_NSIASYNCFILEMETADATA
+  NS_DECL_NSIINPUTSTREAMLENGTH
+  NS_DECL_NSIASYNCINPUTSTREAMLENGTH
+
+  // Create a new lazy RemoteLazyInputStream, and move the provided aInputStream
+  // into storage as referenced by it. May only be called in processes with
+  // RemoteLazyInputStreamStorage.
+  static already_AddRefed<RemoteLazyInputStream> WrapStream(
+      nsIInputStream* aInputStream);
+
+  // mozIRemoteLazyInputStream
+  NS_IMETHOD TakeInternalStream(nsIInputStream** aStream) override;
+  NS_IMETHOD GetInternalStreamID(nsID& aID) override;
+
+ private:
+  friend struct IPC::ParamTraits<mozilla::RemoteLazyInputStream*>;
+
+  // Constructor for an already-closed RemoteLazyInputStream.
+  RemoteLazyInputStream() = default;
+
+  explicit RemoteLazyInputStream(RemoteLazyInputStreamChild* aActor,
+                                 uint64_t aStart = 0,
+                                 uint64_t aLength = UINT64_MAX);
+
+  explicit RemoteLazyInputStream(nsIInputStream* aStream);
+
+  ~RemoteLazyInputStream();
+
+  void StreamNeeded() MOZ_REQUIRES(mMutex);
+
+  // Upon receiving the stream from our actor, we will not wrap it into an async
+  // stream until needed. This allows callers to get access to the underlying
+  // potentially-sync stream using `TakeInternalStream` before reading.
+  nsresult EnsureAsyncRemoteStream() MOZ_REQUIRES(mMutex);
+
+  // Note that data has been read from our input stream, and disconnect from our
+  // remote actor.
+  void MarkConsumed();
+
+  void IPCWrite(IPC::MessageWriter* aWriter);
+  static already_AddRefed<RemoteLazyInputStream> IPCRead(
+      IPC::MessageReader* aReader);
+
+  // Helper method to generate a description of a stream for use in loggging.
+  nsCString Describe() MOZ_REQUIRES(mMutex);
+
+  // Start and length of the slice to apply on this RemoteLazyInputStream when
+  // fetching the underlying stream with `SendStreamNeeded`.
+  const uint64_t mStart = 0;
+  const uint64_t mLength = UINT64_MAX;
+
+  // Any non-const member of this class is protected by mutex because it is
+  // touched on multiple threads.
+  Mutex mMutex{"RemoteLazyInputStream::mMutex"};
+
+  // This is the list of possible states.
+  enum {
+    // The initial state. Only ::Available() can be used without receiving an
+    // error. The available size is known by the actor.
+    eInit,
+
+    // AsyncWait() has been called for the first time. SendStreamNeeded() has
+    // been called and we are waiting for the 'real' inputStream.
+    ePending,
+
+    // When the child receives the stream from the parent, we move to this
+    // state. The received stream is stored in mInnerStream. From now on, any
+    // method call will be forwared to mInnerStream or mAsyncInnerStream.
+    eRunning,
+
+    // If Close() or CloseWithStatus() is called, we move to this state.
+    // mInnerStream is released and any method will return
+    // NS_BASE_STREAM_CLOSED.
+    eClosed,
+  } mState MOZ_GUARDED_BY(mMutex) = eClosed;
+
+  // The actor which will be used to provide the underlying stream or length
+  // information when needed, as well as to efficiently allow transferring the
+  // stream over IPC.
+  //
+  // The connection to our actor will be cleared once the stream has been closed
+  // or has started reading, at which point this stream will be serialized and
+  // cloned as-if it was the underlying stream.
+  RefPtr<RemoteLazyInputStreamChild> mActor MOZ_GUARDED_BY(mMutex);
+
+  nsCOMPtr<nsIInputStream> mInnerStream MOZ_GUARDED_BY(mMutex);
+  nsCOMPtr<nsIAsyncInputStream> mAsyncInnerStream MOZ_GUARDED_BY(mMutex);
+
+  // These 2 values are set only if mState is ePending or eRunning.
+  // RefPtr is used instead of nsCOMPtr to avoid invoking QueryInterface when
+  // assigning in debug builds, as `mInputStreamCallback` may not be threadsafe.
+  RefPtr<nsIInputStreamCallback> mInputStreamCallback MOZ_GUARDED_BY(mMutex);
+  nsCOMPtr<nsIEventTarget> mInputStreamCallbackEventTarget
+      MOZ_GUARDED_BY(mMutex);
+  uint32_t mInputStreamCallbackFlags MOZ_GUARDED_BY(mMutex) = 0;
+  uint32_t mInputStreamCallbackRequestedCount MOZ_GUARDED_BY(mMutex) = 0;
+
+  // These 2 values are set only if mState is ePending.
+  nsCOMPtr<nsIFileMetadataCallback> mFileMetadataCallback
+      MOZ_GUARDED_BY(mMutex);
+  nsCOMPtr<nsIEventTarget> mFileMetadataCallbackEventTarget
+      MOZ_GUARDED_BY(mMutex);
+};
+
+}  // namespace mozilla
+
+template <>
+struct IPC::ParamTraits<mozilla::RemoteLazyInputStream*> {
+  static void Write(IPC::MessageWriter* aWriter,
+                    mozilla::RemoteLazyInputStream* aParam);
+  static bool Read(IPC::MessageReader* aReader,
+                   RefPtr<mozilla::RemoteLazyInputStream>* aResult);
+};
+
+#endif  // mozilla_RemoteLazyInputStream_h
diff --git a/dom/file/ipc/RemoteLazyInputStreamChild.cpp b/dom/file/ipc/RemoteLazyInputStreamChild.cpp
new file mode 100644
index 0000000000..f03aa47aad
--- /dev/null
+++ b/dom/file/ipc/RemoteLazyInputStreamChild.cpp
@@ -0,0 +1,55 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "RemoteLazyInputStreamChild.h"
+#include "RemoteLazyInputStreamThread.h"
+
+namespace mozilla {
+
+extern mozilla::LazyLogModule gRemoteLazyStreamLog;
+
+RemoteLazyInputStreamChild::RemoteLazyInputStreamChild(const nsID& aID)
+    : mID(aID) {}
+
+RemoteLazyInputStreamChild::~RemoteLazyInputStreamChild() = default;
+
+void RemoteLazyInputStreamChild::StreamCreated() {
+  size_t count = ++mStreamCount;
+  MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+          ("Child::StreamCreated %s = %zu", nsIDToCString(mID).get(), count));
+}
+
+void RemoteLazyInputStreamChild::StreamConsumed() {
+  size_t count = --mStreamCount;
+  MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+          ("Child::StreamConsumed %s = %zu", nsIDToCString(mID).get(), count));
+
+  // When the count reaches zero, close the underlying actor.
+  if (count == 0) {
+    auto* t = RemoteLazyInputStreamThread::Get();
+    if (t) {
+      t->Dispatch(
+          NS_NewRunnableFunction("RemoteLazyInputStreamChild::StreamConsumed",
+                                 [self = RefPtr{this}]() {
+                                   if (self->CanSend()) {
+                                     self->SendGoodbye();
+                                   }
+                                 }));
+    }  // else the xpcom thread shutdown has already started.
+  }
+}
+
+void RemoteLazyInputStreamChild::ActorDestroy(ActorDestroyReason aReason) {
+  if (mStreamCount != 0) {
+    NS_WARNING(
+        nsPrintfCString("RemoteLazyInputStreamChild disconnected unexpectedly "
+                        "(%zu streams remaining)! %p %s",
+                        size_t(mStreamCount), this, nsIDToCString(mID).get())
+            .get());
+  }
+}
+
+}  // namespace mozilla
diff --git a/dom/file/ipc/RemoteLazyInputStreamChild.h b/dom/file/ipc/RemoteLazyInputStreamChild.h
new file mode 100644
index 0000000000..c95ed9f058
--- /dev/null
+++ b/dom/file/ipc/RemoteLazyInputStreamChild.h
@@ -0,0 +1,41 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_RemoteLazyInputStreamChild_h
+#define mozilla_RemoteLazyInputStreamChild_h
+
+#include "mozilla/PRemoteLazyInputStreamChild.h"
+
+namespace mozilla {
+
+class RemoteLazyInputStream;
+
+class RemoteLazyInputStreamChild final : public PRemoteLazyInputStreamChild {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(RemoteLazyInputStreamChild, final)
+
+  explicit RemoteLazyInputStreamChild(const nsID& aID);
+
+  const nsID& StreamID() const { return mID; }
+
+  // Manage the count of streams registered on this actor. When the count
+  // reaches 0 the connection to our remote process will be closed.
+  void StreamCreated();
+  void StreamConsumed();
+
+  void ActorDestroy(ActorDestroyReason aReason) override;
+
+ private:
+  ~RemoteLazyInputStreamChild() override;
+
+  const nsID mID;
+
+  std::atomic<size_t> mStreamCount{0};
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_RemoteLazyInputStreamChild_h
diff --git a/dom/file/ipc/RemoteLazyInputStreamParent.cpp b/dom/file/ipc/RemoteLazyInputStreamParent.cpp
new file mode 100644
index 0000000000..d92c529546
--- /dev/null
+++ b/dom/file/ipc/RemoteLazyInputStreamParent.cpp
@@ -0,0 +1,123 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "RemoteLazyInputStreamParent.h"
+#include "RemoteLazyInputStreamStorage.h"
+#include "mozilla/InputStreamLengthHelper.h"
+#include "mozilla/ipc/Endpoint.h"
+#include "mozilla/ipc/IPCStreamUtils.h"
+#include "mozilla/ipc/InputStreamParams.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+#include "nsStreamUtils.h"
+#include "nsServiceManagerUtils.h"
+#include "nsNetCID.h"
+
+namespace mozilla {
+
+extern mozilla::LazyLogModule gRemoteLazyStreamLog;
+
+RemoteLazyInputStreamParent::RemoteLazyInputStreamParent(const nsID& aID)
+    : mID(aID) {
+  auto storage = RemoteLazyInputStreamStorage::Get().unwrapOr(nullptr);
+  if (storage) {
+    storage->ActorCreated(mID);
+  }
+}
+
+void RemoteLazyInputStreamParent::ActorDestroy(
+    IProtocol::ActorDestroyReason aReason) {
+  auto storage = RemoteLazyInputStreamStorage::Get().unwrapOr(nullptr);
+  if (storage) {
+    storage->ActorDestroyed(mID);
+  }
+}
+
+mozilla::ipc::IPCResult RemoteLazyInputStreamParent::RecvClone(
+    mozilla::ipc::Endpoint<PRemoteLazyInputStreamParent>&& aCloneEndpoint) {
+  if (!aCloneEndpoint.IsValid()) {
+    return IPC_FAIL(this, "Unexpected invalid endpoint in RecvClone");
+  }
+
+  MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Debug,
+          ("Parent::RecvClone %s", nsIDToCString(mID).get()));
+
+  auto* newActor = new RemoteLazyInputStreamParent(mID);
+  aCloneEndpoint.Bind(newActor);
+
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult RemoteLazyInputStreamParent::RecvStreamNeeded(
+    uint64_t aStart, uint64_t aLength, StreamNeededResolver&& aResolver) {
+  nsCOMPtr<nsIInputStream> stream;
+  auto storage = RemoteLazyInputStreamStorage::Get().unwrapOr(nullptr);
+  if (storage) {
+    storage->GetStream(mID, aStart, aLength, getter_AddRefs(stream));
+  }
+
+  if (!stream) {
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Warning,
+            ("Parent::RecvStreamNeeded not available! %s",
+             nsIDToCString(mID).get()));
+    aResolver(Nothing());
+    return IPC_OK();
+  }
+
+  Maybe<IPCStream> ipcStream;
+  if (NS_WARN_IF(!SerializeIPCStream(stream.forget(), ipcStream,
+                                     /* aAllowLazy */ false))) {
+    return IPC_FAIL(this, "IPCStream serialization failed!");
+  }
+
+  MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+          ("Parent::RecvStreamNeeded resolve %s", nsIDToCString(mID).get()));
+  aResolver(ipcStream);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult RemoteLazyInputStreamParent::RecvLengthNeeded(
+    LengthNeededResolver&& aResolver) {
+  nsCOMPtr<nsIInputStream> stream;
+  auto storage = RemoteLazyInputStreamStorage::Get().unwrapOr(nullptr);
+  if (storage) {
+    storage->GetStream(mID, 0, UINT64_MAX, getter_AddRefs(stream));
+  }
+
+  if (!stream) {
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Warning,
+            ("Parent::RecvLengthNeeded not available! %s",
+             nsIDToCString(mID).get()));
+    aResolver(-1);
+    return IPC_OK();
+  }
+
+  int64_t length = -1;
+  if (InputStreamLengthHelper::GetSyncLength(stream, &length)) {
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+            ("Parent::RecvLengthNeeded sync resolve %" PRId64 "! %s", length,
+             nsIDToCString(mID).get()));
+    aResolver(length);
+    return IPC_OK();
+  }
+
+  InputStreamLengthHelper::GetAsyncLength(
+      stream, [aResolver, id = mID](int64_t aLength) {
+        MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+                ("Parent::RecvLengthNeeded async resolve %" PRId64 "! %s",
+                 aLength, nsIDToCString(id).get()));
+        aResolver(aLength);
+      });
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult RemoteLazyInputStreamParent::RecvGoodbye() {
+  MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+          ("Parent::RecvGoodbye! %s", nsIDToCString(mID).get()));
+  Close();
+  return IPC_OK();
+}
+
+}  // namespace mozilla
diff --git a/dom/file/ipc/RemoteLazyInputStreamParent.h b/dom/file/ipc/RemoteLazyInputStreamParent.h
new file mode 100644
index 0000000000..cb5b1d4285
--- /dev/null
+++ b/dom/file/ipc/RemoteLazyInputStreamParent.h
@@ -0,0 +1,44 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_RemoteLazyInputStreamParent_h
+#define mozilla_RemoteLazyInputStreamParent_h
+
+#include "mozilla/PRemoteLazyInputStreamParent.h"
+
+class nsIInputStream;
+
+namespace mozilla {
+
+class RemoteLazyInputStreamParent final : public PRemoteLazyInputStreamParent {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(RemoteLazyInputStreamParent, final)
+
+  explicit RemoteLazyInputStreamParent(const nsID& aID);
+
+  const nsID& ID() const { return mID; }
+
+  mozilla::ipc::IPCResult RecvClone(
+      mozilla::ipc::Endpoint<PRemoteLazyInputStreamParent>&& aCloneEndpoint);
+
+  mozilla::ipc::IPCResult RecvStreamNeeded(uint64_t aStart, uint64_t aLength,
+                                           StreamNeededResolver&& aResolver);
+
+  mozilla::ipc::IPCResult RecvLengthNeeded(LengthNeededResolver&& aResolver);
+
+  mozilla::ipc::IPCResult RecvGoodbye();
+
+  void ActorDestroy(IProtocol::ActorDestroyReason aReason) override;
+
+ private:
+  ~RemoteLazyInputStreamParent() override = default;
+
+  const nsID mID;
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_RemoteLazyInputStreamParent_h
diff --git a/dom/file/ipc/RemoteLazyInputStreamStorage.cpp b/dom/file/ipc/RemoteLazyInputStreamStorage.cpp
new file mode 100644
index 0000000000..8ce2c22657
--- /dev/null
+++ b/dom/file/ipc/RemoteLazyInputStreamStorage.cpp
@@ -0,0 +1,243 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/SlicedInputStream.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/StaticMutex.h"
+#include "mozilla/StaticPtr.h"
+#include "nsIPropertyBag2.h"
+#include "nsStreamUtils.h"
+#include "RemoteLazyInputStreamParent.h"
+#include "RemoteLazyInputStreamStorage.h"
+
+namespace mozilla {
+
+using namespace hal;
+
+extern mozilla::LazyLogModule gRemoteLazyStreamLog;
+
+namespace {
+StaticMutex gMutex;
+StaticRefPtr<RemoteLazyInputStreamStorage> gStorage;
+}  // namespace
+
+NS_INTERFACE_MAP_BEGIN(RemoteLazyInputStreamStorage)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIObserver)
+  NS_INTERFACE_MAP_ENTRY(nsIObserver)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_ADDREF(RemoteLazyInputStreamStorage)
+NS_IMPL_RELEASE(RemoteLazyInputStreamStorage)
+
+/* static */
+Result<RefPtr<RemoteLazyInputStreamStorage>, nsresult>
+RemoteLazyInputStreamStorage::Get() {
+  mozilla::StaticMutexAutoLock lock(gMutex);
+  if (gStorage) {
+    RefPtr<RemoteLazyInputStreamStorage> storage = gStorage;
+    return storage;
+  }
+
+  return Err(NS_ERROR_NOT_INITIALIZED);
+}
+
+/* static */
+void RemoteLazyInputStreamStorage::Initialize() {
+  mozilla::StaticMutexAutoLock lock(gMutex);
+  MOZ_ASSERT(!gStorage);
+
+  gStorage = new RemoteLazyInputStreamStorage();
+
+  MOZ_ALWAYS_SUCCEEDS(NS_CreateBackgroundTaskQueue(
+      "RemoteLazyInputStreamStorage", getter_AddRefs(gStorage->mTaskQueue)));
+
+  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
+  if (obs) {
+    obs->AddObserver(gStorage, "xpcom-shutdown", false);
+  }
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStreamStorage::Observe(nsISupports* aSubject, const char* aTopic,
+                                      const char16_t* aData) {
+  MOZ_ASSERT(!strcmp(aTopic, "xpcom-shutdown"));
+
+  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
+  if (obs) {
+    obs->RemoveObserver(this, "xpcom-shutdown");
+  }
+
+  mozilla::StaticMutexAutoLock lock(gMutex);
+  gStorage = nullptr;
+  return NS_OK;
+}
+
+void RemoteLazyInputStreamStorage::AddStream(nsIInputStream* aInputStream,
+                                             const nsID& aID) {
+  MOZ_ASSERT(aInputStream);
+
+  MOZ_LOG(
+      gRemoteLazyStreamLog, LogLevel::Verbose,
+      ("Storage::AddStream(%s) = %p", nsIDToCString(aID).get(), aInputStream));
+
+  UniquePtr<StreamData> data = MakeUnique<StreamData>();
+  data->mInputStream = aInputStream;
+
+  mozilla::StaticMutexAutoLock lock(gMutex);
+  mStorage.InsertOrUpdate(aID, std::move(data));
+}
+
+nsCOMPtr<nsIInputStream> RemoteLazyInputStreamStorage::ForgetStream(
+    const nsID& aID) {
+  MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+          ("Storage::ForgetStream(%s)", nsIDToCString(aID).get()));
+
+  UniquePtr<StreamData> entry;
+
+  mozilla::StaticMutexAutoLock lock(gMutex);
+  mStorage.Remove(aID, &entry);
+
+  if (!entry) {
+    return nullptr;
+  }
+
+  return std::move(entry->mInputStream);
+}
+
+bool RemoteLazyInputStreamStorage::HasStream(const nsID& aID) {
+  mozilla::StaticMutexAutoLock lock(gMutex);
+  StreamData* data = mStorage.Get(aID);
+  return !!data;
+}
+
+void RemoteLazyInputStreamStorage::GetStream(const nsID& aID, uint64_t aStart,
+                                             uint64_t aLength,
+                                             nsIInputStream** aInputStream) {
+  *aInputStream = nullptr;
+
+  MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+          ("Storage::GetStream(%s, %" PRIu64 " %" PRIu64 ")",
+           nsIDToCString(aID).get(), aStart, aLength));
+
+  nsCOMPtr<nsIInputStream> inputStream;
+
+  // NS_CloneInputStream cannot be called when the mutex is locked because it
+  // can, recursively call GetStream() in case the child actor lives on the
+  // parent process.
+  {
+    mozilla::StaticMutexAutoLock lock(gMutex);
+    StreamData* data = mStorage.Get(aID);
+    if (!data) {
+      return;
+    }
+
+    inputStream = data->mInputStream;
+  }
+
+  MOZ_ASSERT(inputStream);
+
+  // We cannot return always the same inputStream because not all of them are
+  // able to be reused. Better to clone them.
+
+  nsCOMPtr<nsIInputStream> clonedStream;
+  nsCOMPtr<nsIInputStream> replacementStream;
+
+  nsresult rv = NS_CloneInputStream(inputStream, getter_AddRefs(clonedStream),
+                                    getter_AddRefs(replacementStream));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return;
+  }
+
+  if (replacementStream) {
+    mozilla::StaticMutexAutoLock lock(gMutex);
+    StreamData* data = mStorage.Get(aID);
+    // data can be gone in the meantime.
+    if (!data) {
+      return;
+    }
+
+    data->mInputStream = replacementStream;
+  }
+
+  // Now it's the right time to apply a slice if needed.
+  if (aStart > 0 || aLength < UINT64_MAX) {
+    clonedStream =
+        new SlicedInputStream(clonedStream.forget(), aStart, aLength);
+  }
+
+  clonedStream.forget(aInputStream);
+}
+
+void RemoteLazyInputStreamStorage::StoreCallback(
+    const nsID& aID, RemoteLazyInputStreamParentCallback* aCallback) {
+  MOZ_ASSERT(aCallback);
+
+  MOZ_LOG(
+      gRemoteLazyStreamLog, LogLevel::Verbose,
+      ("Storage::StoreCallback(%s, %p)", nsIDToCString(aID).get(), aCallback));
+
+  mozilla::StaticMutexAutoLock lock(gMutex);
+  StreamData* data = mStorage.Get(aID);
+  if (data) {
+    MOZ_ASSERT(!data->mCallback);
+    data->mCallback = aCallback;
+  }
+}
+
+already_AddRefed<RemoteLazyInputStreamParentCallback>
+RemoteLazyInputStreamStorage::TakeCallback(const nsID& aID) {
+  MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+          ("Storage::TakeCallback(%s)", nsIDToCString(aID).get()));
+
+  mozilla::StaticMutexAutoLock lock(gMutex);
+  StreamData* data = mStorage.Get(aID);
+  if (!data) {
+    return nullptr;
+  }
+
+  RefPtr<RemoteLazyInputStreamParentCallback> callback;
+  data->mCallback.swap(callback);
+  return callback.forget();
+}
+
+void RemoteLazyInputStreamStorage::ActorCreated(const nsID& aID) {
+  mozilla::StaticMutexAutoLock lock(gMutex);
+  StreamData* data = mStorage.Get(aID);
+  if (!data) {
+    return;
+  }
+
+  size_t count = ++data->mActorCount;
+
+  MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+          ("Storage::ActorCreated(%s) = %zu", nsIDToCString(aID).get(), count));
+}
+
+void RemoteLazyInputStreamStorage::ActorDestroyed(const nsID& aID) {
+  UniquePtr<StreamData> entry;
+  {
+    mozilla::StaticMutexAutoLock lock(gMutex);
+    StreamData* data = mStorage.Get(aID);
+    if (!data) {
+      return;
+    }
+
+    auto newCount = --data->mActorCount;
+    MOZ_LOG(gRemoteLazyStreamLog, LogLevel::Verbose,
+            ("Storage::ActorDestroyed(%s) = %zu (cb=%p)",
+             nsIDToCString(aID).get(), newCount, data->mCallback.get()));
+
+    if (newCount == 0) {
+      mStorage.Remove(aID, &entry);
+    }
+  }
+
+  if (entry && entry->mCallback) {
+    entry->mCallback->ActorDestroyed(aID);
+  }
+}
+
+}  // namespace mozilla
diff --git a/dom/file/ipc/RemoteLazyInputStreamStorage.h b/dom/file/ipc/RemoteLazyInputStreamStorage.h
new file mode 100644
index 0000000000..296a8d9313
--- /dev/null
+++ b/dom/file/ipc/RemoteLazyInputStreamStorage.h
@@ -0,0 +1,78 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_RemoteLazyInputStreamStorage_h
+#define mozilla_RemoteLazyInputStreamStorage_h
+
+#include "mozilla/RefPtr.h"
+#include "nsClassHashtable.h"
+#include "nsIObserver.h"
+
+class nsIInputStream;
+struct nsID;
+
+namespace mozilla {
+
+class NS_NO_VTABLE RemoteLazyInputStreamParentCallback {
+ public:
+  virtual void ActorDestroyed(const nsID& aID) = 0;
+
+  NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
+
+ protected:
+  virtual ~RemoteLazyInputStreamParentCallback() = default;
+};
+
+class RemoteLazyInputStreamStorage final : public nsIObserver {
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIOBSERVER
+
+  // This initializes the singleton and it must be called on the main-thread.
+  static void Initialize();
+
+  static Result<RefPtr<RemoteLazyInputStreamStorage>, nsresult> Get();
+
+  nsISerialEventTarget* TaskQueue() { return mTaskQueue; }
+
+  void AddStream(nsIInputStream* aInputStream, const nsID& aID);
+
+  // Removes and returns the stream corresponding to the nsID. May return a
+  // nullptr if there's no stream stored for the nsID.
+  nsCOMPtr<nsIInputStream> ForgetStream(const nsID& aID);
+
+  bool HasStream(const nsID& aID);
+
+  void GetStream(const nsID& aID, uint64_t aStart, uint64_t aLength,
+                 nsIInputStream** aInputStream);
+
+  void StoreCallback(const nsID& aID,
+                     RemoteLazyInputStreamParentCallback* aCallback);
+
+  already_AddRefed<RemoteLazyInputStreamParentCallback> TakeCallback(
+      const nsID& aID);
+
+  void ActorCreated(const nsID& aID);
+  void ActorDestroyed(const nsID& aID);
+
+ private:
+  RemoteLazyInputStreamStorage() = default;
+  ~RemoteLazyInputStreamStorage() = default;
+
+  nsCOMPtr<nsISerialEventTarget> mTaskQueue;
+
+  struct StreamData {
+    nsCOMPtr<nsIInputStream> mInputStream;
+    RefPtr<RemoteLazyInputStreamParentCallback> mCallback;
+    size_t mActorCount = 0;
+  };
+
+  nsClassHashtable<nsIDHashKey, StreamData> mStorage;
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_RemoteLazyInputStreamStorage_h
diff --git a/dom/file/ipc/RemoteLazyInputStreamThread.cpp b/dom/file/ipc/RemoteLazyInputStreamThread.cpp
new file mode 100644
index 0000000000..ec6c99952b
--- /dev/null
+++ b/dom/file/ipc/RemoteLazyInputStreamThread.cpp
@@ -0,0 +1,237 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "RemoteLazyInputStreamThread.h"
+
+#include "ErrorList.h"
+#include "mozilla/AppShutdown.h"
+#include "mozilla/SchedulerGroup.h"
+#include "mozilla/StaticMutex.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/TaskCategory.h"
+#include "mozilla/ipc/BackgroundChild.h"
+#include "mozilla/ipc/PBackgroundChild.h"
+#include "nsXPCOMPrivate.h"
+
+using namespace mozilla::ipc;
+
+namespace mozilla {
+
+namespace {
+
+StaticMutex gRemoteLazyThreadMutex;
+StaticRefPtr<RemoteLazyInputStreamThread> gRemoteLazyThread;
+
+class ThreadInitializeRunnable final : public Runnable {
+ public:
+  ThreadInitializeRunnable() : Runnable("dom::ThreadInitializeRunnable") {}
+
+  NS_IMETHOD
+  Run() override {
+    StaticMutexAutoLock lock(gRemoteLazyThreadMutex);
+    MOZ_ASSERT(gRemoteLazyThread);
+    if (NS_WARN_IF(!gRemoteLazyThread->InitializeOnMainThread())) {
+      // RemoteLazyInputStreamThread::GetOrCreate might have handed out a
+      // pointer to our thread already at this point such that we cannot
+      // just do gRemoteLazyThread = nullptr; here.
+      MOZ_DIAGNOSTIC_ASSERT(
+          false, "Async gRemoteLazyThread->InitializeOnMainThread() failed.");
+      return NS_ERROR_FAILURE;
+    }
+    return NS_OK;
+  }
+};
+
+}  // namespace
+
+NS_IMPL_ISUPPORTS(RemoteLazyInputStreamThread, nsIObserver, nsIEventTarget,
+                  nsISerialEventTarget, nsIDirectTaskDispatcher)
+
+bool RLISThreadIsInOrBeyondShutdown() {
+  // ShutdownPhase::XPCOMShutdownThreads matches
+  // obs->AddObserver(this, NS_XPCOM_SHUTDOWN_THREADS_OBSERVER_ID, false);
+  return AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMShutdownThreads);
+}
+
+/* static */
+RemoteLazyInputStreamThread* RemoteLazyInputStreamThread::Get() {
+  if (RLISThreadIsInOrBeyondShutdown()) {
+    return nullptr;
+  }
+
+  StaticMutexAutoLock lock(gRemoteLazyThreadMutex);
+
+  return gRemoteLazyThread;
+}
+
+/* static */
+RemoteLazyInputStreamThread* RemoteLazyInputStreamThread::GetOrCreate() {
+  if (RLISThreadIsInOrBeyondShutdown()) {
+    return nullptr;
+  }
+
+  StaticMutexAutoLock lock(gRemoteLazyThreadMutex);
+
+  if (!gRemoteLazyThread) {
+    gRemoteLazyThread = new RemoteLazyInputStreamThread();
+    if (!gRemoteLazyThread->Initialize()) {
+      gRemoteLazyThread = nullptr;
+    }
+  }
+
+  return gRemoteLazyThread;
+}
+
+bool RemoteLazyInputStreamThread::Initialize() {
+  nsCOMPtr<nsIThread> thread;
+  nsresult rv = NS_NewNamedThread("RemoteLzyStream", getter_AddRefs(thread));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return false;
+  }
+
+  mThread = thread;
+
+  if (!NS_IsMainThread()) {
+    RefPtr<Runnable> runnable = new ThreadInitializeRunnable();
+    nsresult rv =
+        SchedulerGroup::Dispatch(TaskCategory::Other, runnable.forget());
+    return !NS_WARN_IF(NS_FAILED(rv));
+  }
+
+  return InitializeOnMainThread();
+}
+
+bool RemoteLazyInputStreamThread::InitializeOnMainThread() {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
+  if (NS_WARN_IF(!obs)) {
+    return false;
+  }
+
+  nsresult rv =
+      obs->AddObserver(this, NS_XPCOM_SHUTDOWN_THREADS_OBSERVER_ID, false);
+  return !NS_WARN_IF(NS_FAILED(rv));
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStreamThread::Observe(nsISupports* aSubject, const char* aTopic,
+                                     const char16_t* aData) {
+  MOZ_ASSERT(!strcmp(aTopic, NS_XPCOM_SHUTDOWN_THREADS_OBSERVER_ID));
+
+  StaticMutexAutoLock lock(gRemoteLazyThreadMutex);
+
+  if (mThread) {
+    mThread->Shutdown();
+    mThread = nullptr;
+  }
+
+  gRemoteLazyThread = nullptr;
+
+  return NS_OK;
+}
+
+// nsIEventTarget
+
+NS_IMETHODIMP_(bool)
+RemoteLazyInputStreamThread::IsOnCurrentThreadInfallible() {
+  return mThread->IsOnCurrentThread();
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStreamThread::IsOnCurrentThread(bool* aRetval) {
+  return mThread->IsOnCurrentThread(aRetval);
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStreamThread::Dispatch(already_AddRefed<nsIRunnable> aRunnable,
+                                      uint32_t aFlags) {
+  if (RLISThreadIsInOrBeyondShutdown()) {
+    return NS_ERROR_ILLEGAL_DURING_SHUTDOWN;
+  }
+
+  nsCOMPtr<nsIRunnable> runnable(aRunnable);
+
+  StaticMutexAutoLock lock(gRemoteLazyThreadMutex);
+
+  return mThread->Dispatch(runnable.forget(), aFlags);
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStreamThread::DispatchFromScript(nsIRunnable* aRunnable,
+                                                uint32_t aFlags) {
+  nsCOMPtr<nsIRunnable> runnable(aRunnable);
+  return Dispatch(runnable.forget(), aFlags);
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStreamThread::DelayedDispatch(already_AddRefed<nsIRunnable>,
+                                             uint32_t) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStreamThread::RegisterShutdownTask(nsITargetShutdownTask*) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStreamThread::UnregisterShutdownTask(nsITargetShutdownTask*) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStreamThread::DispatchDirectTask(
+    already_AddRefed<nsIRunnable> aRunnable) {
+  nsCOMPtr<nsIRunnable> runnable(aRunnable);
+
+  StaticMutexAutoLock lock(gRemoteLazyThreadMutex);
+
+  nsCOMPtr<nsIDirectTaskDispatcher> dispatcher = do_QueryInterface(mThread);
+
+  if (dispatcher) {
+    return dispatcher->DispatchDirectTask(runnable.forget());
+  }
+
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP RemoteLazyInputStreamThread::DrainDirectTasks() {
+  StaticMutexAutoLock lock(gRemoteLazyThreadMutex);
+
+  nsCOMPtr<nsIDirectTaskDispatcher> dispatcher = do_QueryInterface(mThread);
+
+  if (dispatcher) {
+    return dispatcher->DrainDirectTasks();
+  }
+
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP RemoteLazyInputStreamThread::HaveDirectTasks(bool* aValue) {
+  StaticMutexAutoLock lock(gRemoteLazyThreadMutex);
+
+  nsCOMPtr<nsIDirectTaskDispatcher> dispatcher = do_QueryInterface(mThread);
+
+  if (dispatcher) {
+    return dispatcher->HaveDirectTasks(aValue);
+  }
+
+  return NS_ERROR_FAILURE;
+}
+
+bool IsOnDOMFileThread() {
+  MOZ_ASSERT(!RLISThreadIsInOrBeyondShutdown());
+
+  StaticMutexAutoLock lock(gRemoteLazyThreadMutex);
+  MOZ_ASSERT(gRemoteLazyThread);
+
+  return gRemoteLazyThread->IsOnCurrentThreadInfallible();
+}
+
+void AssertIsOnDOMFileThread() { MOZ_ASSERT(IsOnDOMFileThread()); }
+
+}  // namespace mozilla
diff --git a/dom/file/ipc/RemoteLazyInputStreamThread.h b/dom/file/ipc/RemoteLazyInputStreamThread.h
new file mode 100644
index 0000000000..378cb09009
--- /dev/null
+++ b/dom/file/ipc/RemoteLazyInputStreamThread.h
@@ -0,0 +1,52 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_RemoteLazyInputStreamThread_h
+#define mozilla_RemoteLazyInputStreamThread_h
+
+#include "mozilla/RemoteLazyInputStreamChild.h"
+#include "nsIEventTarget.h"
+#include "nsIObserver.h"
+#include "nsTArray.h"
+
+class nsIThread;
+
+namespace mozilla {
+
+class RemoteLazyInputStreamChild;
+
+// XXX Rename this class since it's used by LSNG too.
+class RemoteLazyInputStreamThread final : public nsIObserver,
+                                          public nsISerialEventTarget,
+                                          public nsIDirectTaskDispatcher {
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIOBSERVER
+  NS_DECL_NSIEVENTTARGET
+  NS_DECL_NSISERIALEVENTTARGET
+  NS_DECL_NSIDIRECTTASKDISPATCHER
+
+  static RemoteLazyInputStreamThread* Get();
+
+  static RemoteLazyInputStreamThread* GetOrCreate();
+
+  bool Initialize();
+
+  bool InitializeOnMainThread();
+
+ private:
+  ~RemoteLazyInputStreamThread() = default;
+
+  nsCOMPtr<nsIThread> mThread;
+};
+
+bool IsOnDOMFileThread();
+
+void AssertIsOnDOMFileThread();
+
+}  // namespace mozilla
+
+#endif  // mozilla_RemoteLazyInputStreamThread_h
diff --git a/dom/file/ipc/TemporaryIPCBlobChild.cpp b/dom/file/ipc/TemporaryIPCBlobChild.cpp
new file mode 100644
index 0000000000..7c7df55d81
--- /dev/null
+++ b/dom/file/ipc/TemporaryIPCBlobChild.cpp
@@ -0,0 +1,86 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "TemporaryIPCBlobChild.h"
+#include "mozilla/dom/BlobImpl.h"
+#include "mozilla/dom/MutableBlobStorage.h"
+#include "mozilla/dom/IPCBlobUtils.h"
+#include <private/pprio.h>
+
+namespace mozilla::dom {
+
+TemporaryIPCBlobChild::TemporaryIPCBlobChild(MutableBlobStorage* aStorage)
+    : mMutableBlobStorage(aStorage), mActive(true) {
+  MOZ_ASSERT(aStorage);
+}
+
+TemporaryIPCBlobChild::~TemporaryIPCBlobChild() = default;
+
+mozilla::ipc::IPCResult TemporaryIPCBlobChild::RecvFileDesc(
+    const FileDescriptor& aFD) {
+  MOZ_ASSERT(mActive);
+
+  auto rawFD = aFD.ClonePlatformHandle();
+  PRFileDesc* prfile = PR_ImportFile(PROsfd(rawFD.release()));
+
+  mMutableBlobStorage->TemporaryFileCreated(prfile);
+  mMutableBlobStorage = nullptr;
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult TemporaryIPCBlobChild::Recv__delete__(
+    const IPCBlobOrError& aBlobOrError) {
+  mActive = false;
+  mMutableBlobStorage = nullptr;
+
+  if (aBlobOrError.type() == IPCBlobOrError::TIPCBlob) {
+    // This must be always deserialized.
+    RefPtr<BlobImpl> blobImpl =
+        IPCBlobUtils::Deserialize(aBlobOrError.get_IPCBlob());
+    MOZ_ASSERT(blobImpl);
+
+    if (mCallback) {
+      mCallback->OperationSucceeded(blobImpl);
+    }
+  } else if (mCallback) {
+    MOZ_ASSERT(aBlobOrError.type() == IPCBlobOrError::Tnsresult);
+    mCallback->OperationFailed(aBlobOrError.get_nsresult());
+  }
+
+  mCallback = nullptr;
+
+  return IPC_OK();
+}
+
+void TemporaryIPCBlobChild::ActorDestroy(ActorDestroyReason aWhy) {
+  mActive = false;
+  mMutableBlobStorage = nullptr;
+
+  if (mCallback) {
+    mCallback->OperationFailed(NS_ERROR_FAILURE);
+    mCallback = nullptr;
+  }
+}
+
+void TemporaryIPCBlobChild::AskForBlob(TemporaryIPCBlobChildCallback* aCallback,
+                                       const nsACString& aContentType,
+                                       PRFileDesc* aFD) {
+  MOZ_ASSERT(aCallback);
+  MOZ_ASSERT(!mCallback);
+
+  if (!mActive) {
+    aCallback->OperationFailed(NS_ERROR_FAILURE);
+    return;
+  }
+
+  FileDescriptor fdd = FileDescriptor(
+      FileDescriptor::PlatformHandleType(PR_FileDesc2NativeHandle(aFD)));
+
+  mCallback = aCallback;
+  SendOperationDone(aContentType, fdd);
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/ipc/TemporaryIPCBlobChild.h b/dom/file/ipc/TemporaryIPCBlobChild.h
new file mode 100644
index 0000000000..a909ee0d53
--- /dev/null
+++ b/dom/file/ipc/TemporaryIPCBlobChild.h
@@ -0,0 +1,53 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_TemporaryIPCBlobChild_h
+#define mozilla_dom_TemporaryIPCBlobChild_h
+
+#include "mozilla/dom/PTemporaryIPCBlob.h"
+#include "mozilla/dom/PTemporaryIPCBlobChild.h"
+
+namespace mozilla::dom {
+
+class BlobImpl;
+class MutableBlobStorage;
+
+class TemporaryIPCBlobChildCallback {
+ public:
+  NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
+
+  virtual void OperationSucceeded(BlobImpl* aBlobImpl) = 0;
+  virtual void OperationFailed(nsresult aRv) = 0;
+};
+
+class TemporaryIPCBlobChild final : public PTemporaryIPCBlobChild {
+  friend class PTemporaryIPCBlobChild;
+
+ public:
+  NS_INLINE_DECL_REFCOUNTING(TemporaryIPCBlobChild)
+
+  explicit TemporaryIPCBlobChild(MutableBlobStorage* aStorage);
+
+  void AskForBlob(TemporaryIPCBlobChildCallback* aCallback,
+                  const nsACString& aContentType, PRFileDesc* aFD);
+
+ private:
+  ~TemporaryIPCBlobChild() override;
+
+  mozilla::ipc::IPCResult RecvFileDesc(const FileDescriptor& aFD);
+
+  mozilla::ipc::IPCResult Recv__delete__(const IPCBlobOrError& aBlobOrError);
+
+  void ActorDestroy(ActorDestroyReason aWhy) override;
+
+  RefPtr<MutableBlobStorage> mMutableBlobStorage;
+  RefPtr<TemporaryIPCBlobChildCallback> mCallback;
+  bool mActive;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_TemporaryIPCBlobChild_h
diff --git a/dom/file/ipc/TemporaryIPCBlobParent.cpp b/dom/file/ipc/TemporaryIPCBlobParent.cpp
new file mode 100644
index 0000000000..d742859aa9
--- /dev/null
+++ b/dom/file/ipc/TemporaryIPCBlobParent.cpp
@@ -0,0 +1,102 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "private/pprio.h"
+#include "TemporaryIPCBlobParent.h"
+#include "mozilla/dom/FileBlobImpl.h"
+#include "nsAnonymousTemporaryFile.h"
+#include "TemporaryFileBlobImpl.h"
+#include "mozilla/dom/IPCBlobUtils.h"
+
+namespace mozilla::dom {
+
+TemporaryIPCBlobParent::TemporaryIPCBlobParent() : mActive(true) {}
+
+TemporaryIPCBlobParent::~TemporaryIPCBlobParent() {
+  // If we still have mFile, let's remove it.
+  if (mFile) {
+    mFile->Remove(false);
+  }
+}
+
+mozilla::ipc::IPCResult TemporaryIPCBlobParent::CreateAndShareFile() {
+  MOZ_ASSERT(mActive);
+  MOZ_ASSERT(!mFile);
+
+  nsresult rv = NS_OpenAnonymousTemporaryNsIFile(getter_AddRefs(mFile));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return SendDeleteError(rv);
+  }
+
+  PRFileDesc* fd;
+  rv = mFile->OpenNSPRFileDesc(PR_RDWR, PR_IRWXU, &fd);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return SendDeleteError(rv);
+  }
+
+  FileDescriptor fdd = FileDescriptor(
+      FileDescriptor::PlatformHandleType(PR_FileDesc2NativeHandle(fd)));
+
+  // The FileDescriptor object owns a duplicate of the file handle; we
+  // must close the original (and clean up the NSPR descriptor).
+  PR_Close(fd);
+
+  Unused << SendFileDesc(fdd);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult TemporaryIPCBlobParent::RecvOperationFailed() {
+  MOZ_ASSERT(mActive);
+  mActive = false;
+
+  // Nothing to do.
+  Unused << Send__delete__(this, NS_ERROR_FAILURE);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult TemporaryIPCBlobParent::RecvOperationDone(
+    const nsCString& aContentType, const FileDescriptor& aFD) {
+  MOZ_ASSERT(mActive);
+  mActive = false;
+
+  // We have received a file descriptor because in this way we have kept the
+  // file locked on windows during the IPC communication. After the creation of
+  // the TemporaryFileBlobImpl, this prfile can be closed.
+  auto rawFD = aFD.ClonePlatformHandle();
+  PRFileDesc* prfile = PR_ImportFile(PROsfd(rawFD.release()));
+
+  // Let's create the BlobImpl.
+  nsCOMPtr<nsIFile> file = std::move(mFile);
+
+  RefPtr<TemporaryFileBlobImpl> blobImpl =
+      new TemporaryFileBlobImpl(file, NS_ConvertUTF8toUTF16(aContentType));
+
+  PR_Close(prfile);
+
+  IPCBlob ipcBlob;
+  nsresult rv = IPCBlobUtils::Serialize(blobImpl, ipcBlob);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    Unused << Send__delete__(this, NS_ERROR_FAILURE);
+    return IPC_OK();
+  }
+
+  Unused << Send__delete__(this, ipcBlob);
+  return IPC_OK();
+}
+
+void TemporaryIPCBlobParent::ActorDestroy(ActorDestroyReason aWhy) {
+  mActive = false;
+}
+
+mozilla::ipc::IPCResult TemporaryIPCBlobParent::SendDeleteError(nsresult aRv) {
+  MOZ_ASSERT(mActive);
+  mActive = false;
+
+  Unused << Send__delete__(this, aRv);
+  return IPC_OK();
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/ipc/TemporaryIPCBlobParent.h b/dom/file/ipc/TemporaryIPCBlobParent.h
new file mode 100644
index 0000000000..2609e8d820
--- /dev/null
+++ b/dom/file/ipc/TemporaryIPCBlobParent.h
@@ -0,0 +1,43 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_TemporaryIPCBlobParent_h
+#define mozilla_dom_TemporaryIPCBlobParent_h
+
+#include "mozilla/dom/PTemporaryIPCBlob.h"
+#include "mozilla/dom/PTemporaryIPCBlobParent.h"
+
+class nsIFile;
+
+namespace mozilla::dom {
+
+class TemporaryIPCBlobParent final : public PTemporaryIPCBlobParent {
+  friend class PTemporaryIPCBlobParent;
+
+ public:
+  explicit TemporaryIPCBlobParent();
+
+  mozilla::ipc::IPCResult CreateAndShareFile();
+
+ private:
+  ~TemporaryIPCBlobParent() override;
+
+  mozilla::ipc::IPCResult RecvOperationFailed();
+
+  mozilla::ipc::IPCResult RecvOperationDone(const nsCString& aContentType,
+                                            const FileDescriptor& aFD);
+
+  void ActorDestroy(ActorDestroyReason aWhy) override;
+
+  mozilla::ipc::IPCResult SendDeleteError(nsresult aRv);
+
+  nsCOMPtr<nsIFile> mFile;
+  bool mActive;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_TemporaryIPCBlobParent_h
diff --git a/dom/file/ipc/moz.build b/dom/file/ipc/moz.build
new file mode 100644
index 0000000000..21c2d50cac
--- /dev/null
+++ b/dom/file/ipc/moz.build
@@ -0,0 +1,69 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+with Files("**"):
+    BUG_COMPONENT = ("Core", "DOM: File")
+
+XPIDL_SOURCES += [
+    "mozIRemoteLazyInputStream.idl",
+]
+
+XPIDL_MODULE = "dom"
+
+EXPORTS.mozilla.dom += [
+    "FileCreatorChild.h",
+    "FileCreatorParent.h",
+    "IPCBlobUtils.h",
+    "TemporaryIPCBlobChild.h",
+    "TemporaryIPCBlobParent.h",
+]
+
+EXPORTS.mozilla += [
+    "RemoteLazyInputStream.h",
+    "RemoteLazyInputStreamChild.h",
+    "RemoteLazyInputStreamParent.h",
+    "RemoteLazyInputStreamStorage.h",
+    "RemoteLazyInputStreamThread.h",
+]
+
+UNIFIED_SOURCES += [
+    "FileCreatorChild.cpp",
+    "FileCreatorParent.cpp",
+    "IPCBlobUtils.cpp",
+    "RemoteLazyInputStream.cpp",
+    "RemoteLazyInputStreamChild.cpp",
+    "RemoteLazyInputStreamParent.cpp",
+    "RemoteLazyInputStreamStorage.cpp",
+    "RemoteLazyInputStreamThread.cpp",
+    "TemporaryIPCBlobChild.cpp",
+    "TemporaryIPCBlobParent.cpp",
+]
+
+IPDL_SOURCES += [
+    "IPCBlob.ipdlh",
+    "PFileCreator.ipdl",
+    "PRemoteLazyInputStream.ipdl",
+    "PTemporaryIPCBlob.ipdl",
+]
+
+LOCAL_INCLUDES += [
+    "/dom/file",
+    "/dom/ipc",
+    "/xpcom/build",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+# Add libFuzzer configuration directives
+include("/tools/fuzzing/libfuzzer-config.mozbuild")
+
+FINAL_LIBRARY = "xul"
+
+if CONFIG["MOZ_WIDGET_TOOLKIT"] == "gtk":
+    CXXFLAGS += CONFIG["MOZ_GTK3_CFLAGS"]
+
+BROWSER_CHROME_MANIFESTS += ["tests/browser.ini"]
+MOCHITEST_MANIFESTS += ["tests/mochitest.ini"]
diff --git a/dom/file/ipc/mozIRemoteLazyInputStream.idl b/dom/file/ipc/mozIRemoteLazyInputStream.idl
new file mode 100644
index 0000000000..8303b2e0fc
--- /dev/null
+++ b/dom/file/ipc/mozIRemoteLazyInputStream.idl
@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+interface nsIInputStream;
+
+/*
+ * A simple interface to get the underlying stream from an
+ * RemoteLazyInputStream.
+ */
+[scriptable, builtinclass, uuid(4125585f-b0c2-4964-a83c-4b0d99f26d49)]
+interface mozIRemoteLazyInputStream : nsISupports
+{
+  /**
+   * Attempts to take the internal stream out of this mozIRemoteLazyInputStream.
+   * Throws NS_BASE_STREAM_WOULD_BLOCK if the stream isn't available yet, and
+   * NS_BASE_STREAM_CLOSED if it was already closed.
+   */
+  [noscript] nsIInputStream TakeInternalStream();
+
+  /**
+   * If this RemoteLazyInputStream is actively backed by an actor, get the
+   * underlying actor's ID. Will throw if the underlying actor is no longer
+   * available.
+   */
+  [noscript] readonly attribute nsIDRef internalStreamID;
+};
diff --git a/dom/file/ipc/tests/browser.ini b/dom/file/ipc/tests/browser.ini
new file mode 100644
index 0000000000..f6fcdc37a4
--- /dev/null
+++ b/dom/file/ipc/tests/browser.ini
@@ -0,0 +1,7 @@
+[DEFAULT]
+support-files =
+  empty.html
+
+[browser_ipcBlob.js]
+[browser_ipcBlob_temporary.js]
+support-files = temporary.sjs
diff --git a/dom/file/ipc/tests/browser_ipcBlob.js b/dom/file/ipc/tests/browser_ipcBlob.js
new file mode 100644
index 0000000000..3ba0f05c90
--- /dev/null
+++ b/dom/file/ipc/tests/browser_ipcBlob.js
@@ -0,0 +1,251 @@
+/* -*- Mode: javascript; tab-width: 2; indent-tabs-mode: nil; js-indent-level: 2 -*- */
+
+requestLongerTimeout(3);
+
+const BASE_URI = "http://mochi.test:8888/browser/dom/file/ipc/tests/empty.html";
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["privacy.partition.bloburl_per_agent_cluster", false]],
+  });
+});
+
+// More than 1mb memory blob childA-parent-childB.
+add_task(async function test_CtoPtoC_big() {
+  let tab1 = await BrowserTestUtils.openNewForegroundTab(gBrowser, BASE_URI);
+  let browser1 = gBrowser.getBrowserForTab(tab1);
+
+  let blob = await SpecialPowers.spawn(browser1, [], function() {
+    Cu.importGlobalProperties(["Blob"]);
+    let blob = new Blob([new Array(1024 * 1024).join("123456789ABCDEF")]);
+    return blob;
+  });
+
+  ok(blob, "CtoPtoC-big: We have a blob!");
+  is(
+    blob.size,
+    new Array(1024 * 1024).join("123456789ABCDEF").length,
+    "CtoPtoC-big: The size matches"
+  );
+
+  let tab2 = await BrowserTestUtils.openNewForegroundTab(gBrowser, BASE_URI);
+  let browser2 = gBrowser.getBrowserForTab(tab2);
+
+  let status = await SpecialPowers.spawn(browser2, [blob], function(blob) {
+    return new Promise(resolve => {
+      let fr = new content.FileReader();
+      fr.readAsText(blob);
+      fr.onloadend = function() {
+        resolve(fr.result == new Array(1024 * 1024).join("123456789ABCDEF"));
+      };
+    });
+  });
+
+  ok(status, "CtoPtoC-big: Data match!");
+
+  BrowserTestUtils.removeTab(tab1);
+  BrowserTestUtils.removeTab(tab2);
+});
+
+// Less than 1mb memory blob childA-parent-childB.
+add_task(async function test_CtoPtoC_small() {
+  let tab1 = await BrowserTestUtils.openNewForegroundTab(gBrowser, BASE_URI);
+  let browser1 = gBrowser.getBrowserForTab(tab1);
+
+  let blob = await SpecialPowers.spawn(browser1, [], function() {
+    Cu.importGlobalProperties(["Blob"]);
+    let blob = new Blob(["hello world!"]);
+    return blob;
+  });
+
+  ok(blob, "CtoPtoC-small: We have a blob!");
+  is(blob.size, "hello world!".length, "CtoPtoC-small: The size matches");
+
+  let tab2 = await BrowserTestUtils.openNewForegroundTab(gBrowser, BASE_URI);
+  let browser2 = gBrowser.getBrowserForTab(tab2);
+
+  let status = await SpecialPowers.spawn(browser2, [blob], function(blob) {
+    return new Promise(resolve => {
+      let fr = new content.FileReader();
+      fr.readAsText(blob);
+      fr.onloadend = function() {
+        resolve(fr.result == "hello world!");
+      };
+    });
+  });
+
+  ok(status, "CtoPtoC-small: Data match!");
+
+  BrowserTestUtils.removeTab(tab1);
+  BrowserTestUtils.removeTab(tab2);
+});
+
+// More than 1mb memory blob childA-parent-childB: BroadcastChannel
+add_task(async function test_CtoPtoC_bc_big() {
+  let tab1 = await BrowserTestUtils.openNewForegroundTab(gBrowser, BASE_URI);
+  let browser1 = gBrowser.getBrowserForTab(tab1);
+
+  await SpecialPowers.spawn(browser1, [], function() {
+    Cu.importGlobalProperties(["Blob"]);
+    var bc = new content.BroadcastChannel("test");
+    bc.onmessage = function() {
+      bc.postMessage(
+        new Blob([new Array(1024 * 1024).join("123456789ABCDEF")])
+      );
+    };
+  });
+
+  let tab2 = await BrowserTestUtils.openNewForegroundTab(gBrowser, BASE_URI);
+  let browser2 = gBrowser.getBrowserForTab(tab2);
+
+  let status = await SpecialPowers.spawn(browser2, [], function() {
+    return new Promise(resolve => {
+      var bc = new content.BroadcastChannel("test");
+      bc.onmessage = function(e) {
+        let fr = new content.FileReader();
+        fr.readAsText(e.data);
+        fr.onloadend = function() {
+          resolve(fr.result == new Array(1024 * 1024).join("123456789ABCDEF"));
+        };
+      };
+
+      bc.postMessage("GO!");
+    });
+  });
+
+  ok(status, "CtoPtoC-broadcastChannel-big: Data match!");
+
+  BrowserTestUtils.removeTab(tab1);
+  BrowserTestUtils.removeTab(tab2);
+});
+
+// Less than 1mb memory blob childA-parent-childB: BroadcastChannel
+add_task(async function test_CtoPtoC_bc_small() {
+  let tab1 = await BrowserTestUtils.openNewForegroundTab(gBrowser, BASE_URI);
+  let browser1 = gBrowser.getBrowserForTab(tab1);
+
+  await SpecialPowers.spawn(browser1, [], function() {
+    Cu.importGlobalProperties(["Blob"]);
+    var bc = new content.BroadcastChannel("test");
+    bc.onmessage = function() {
+      bc.postMessage(new Blob(["hello world!"]));
+    };
+  });
+
+  let tab2 = await BrowserTestUtils.openNewForegroundTab(gBrowser, BASE_URI);
+  let browser2 = gBrowser.getBrowserForTab(tab2);
+
+  let status = await SpecialPowers.spawn(browser2, [], function() {
+    return new Promise(resolve => {
+      var bc = new content.BroadcastChannel("test");
+      bc.onmessage = function(e) {
+        let fr = new content.FileReader();
+        fr.readAsText(e.data);
+        fr.onloadend = function() {
+          resolve(fr.result == "hello world!");
+        };
+      };
+
+      bc.postMessage("GO!");
+    });
+  });
+
+  ok(status, "CtoPtoC-broadcastChannel-small: Data match!");
+
+  BrowserTestUtils.removeTab(tab1);
+  BrowserTestUtils.removeTab(tab2);
+});
+
+// blob URL childA-parent-childB
+add_task(async function test_CtoPtoC_bc_small() {
+  let tab1 = await BrowserTestUtils.openNewForegroundTab(gBrowser, BASE_URI);
+  let browser1 = gBrowser.getBrowserForTab(tab1);
+
+  let blobURL = await SpecialPowers.spawn(browser1, [], function() {
+    Cu.importGlobalProperties(["Blob"]);
+    return content.URL.createObjectURL(new content.Blob(["hello world!"]));
+  });
+
+  let tab2 = await BrowserTestUtils.openNewForegroundTab(gBrowser, BASE_URI);
+  let browser2 = gBrowser.getBrowserForTab(tab2);
+
+  let status = await SpecialPowers.spawn(browser2, [blobURL], function(
+    blobURL
+  ) {
+    return new Promise(resolve => {
+      var xhr = new content.XMLHttpRequest();
+      xhr.open("GET", blobURL);
+      xhr.onloadend = function() {
+        resolve(xhr.response == "hello world!");
+      };
+
+      xhr.send();
+    });
+  });
+
+  ok(status, "CtoPtoC-blobURL: Data match!");
+
+  BrowserTestUtils.removeTab(tab1);
+  BrowserTestUtils.removeTab(tab2);
+});
+
+// Multipart Blob childA-parent-childB.
+add_task(async function test_CtoPtoC_multipart() {
+  let tab1 = await BrowserTestUtils.openNewForegroundTab(gBrowser, BASE_URI);
+  let browser1 = gBrowser.getBrowserForTab(tab1);
+
+  let blob = await SpecialPowers.spawn(browser1, [], function() {
+    Cu.importGlobalProperties(["Blob"]);
+    return new Blob(["!"]);
+  });
+
+  ok(blob, "CtoPtoC-multipart: We have a blob!");
+  is(blob.size, "!".length, "CtoPtoC-multipart: The size matches");
+
+  let newBlob = new Blob(["world", blob]);
+
+  let tab2 = await BrowserTestUtils.openNewForegroundTab(gBrowser, BASE_URI);
+  let browser2 = gBrowser.getBrowserForTab(tab2);
+
+  let status = await SpecialPowers.spawn(browser2, [newBlob], function(blob) {
+    Cu.importGlobalProperties(["Blob"]);
+    return new Promise(resolve => {
+      let fr = new content.FileReader();
+      fr.readAsText(new Blob(["hello ", blob]));
+      fr.onloadend = function() {
+        resolve(fr.result == "hello world!");
+      };
+    });
+  });
+
+  ok(status, "CtoPtoC-multipart: Data match!");
+
+  BrowserTestUtils.removeTab(tab1);
+  BrowserTestUtils.removeTab(tab2);
+});
+
+// Multipart Blob childA-parent with a max size
+add_task(async function test_CtoPsize_multipart() {
+  let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, BASE_URI);
+  let browser = gBrowser.getBrowserForTab(tab);
+
+  let blob = await SpecialPowers.spawn(browser, [], function() {
+    Cu.importGlobalProperties(["Blob"]);
+
+    let data = new Array(1024 * 512).join("A");
+    let blob1 = new Blob([data]);
+    let blob2 = new Blob([data]);
+    let blob3 = new Blob([data]);
+
+    return new Blob([blob1, blob2, blob3]);
+  });
+
+  ok(blob, "CtoPsize-multipart: We have a blob!");
+  is(
+    blob.size,
+    new Array(1024 * 512).join("A").length * 3,
+    "CtoPsize-multipart: The size matches"
+  );
+
+  BrowserTestUtils.removeTab(tab);
+});
diff --git a/dom/file/ipc/tests/browser_ipcBlob_temporary.js b/dom/file/ipc/tests/browser_ipcBlob_temporary.js
new file mode 100644
index 0000000000..c2d9d54e87
--- /dev/null
+++ b/dom/file/ipc/tests/browser_ipcBlob_temporary.js
@@ -0,0 +1,115 @@
+/* -*- Mode: javascript; tab-width: 2; indent-tabs-mode: nil; js-indent-level: 2 -*- */
+
+requestLongerTimeout(3);
+
+const BASE_URI = "http://mochi.test:8888/browser/dom/file/ipc/tests/empty.html";
+
+add_task(async function test() {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["dom.blob.memoryToTemporaryFile", 1],
+      ["dom.ipc.processCount", 4],
+    ],
+  });
+
+  let tab1 = await BrowserTestUtils.openNewForegroundTab(gBrowser, BASE_URI);
+  let browser1 = gBrowser.getBrowserForTab(tab1);
+
+  let tab2 = await BrowserTestUtils.openNewForegroundTab(gBrowser, BASE_URI);
+  let browser2 = gBrowser.getBrowserForTab(tab2);
+
+  await SpecialPowers.spawn(browser2, [], function() {
+    content.window.testPromise = new content.window.Promise(resolve => {
+      let bc = new content.window.BroadcastChannel("foobar");
+      bc.onmessage = e => {
+        function realTest() {
+          return new content.window.Promise(resolve => {
+            let count = 10;
+            for (let i = 0; i < count; ++i) {
+              info("FileReader at the same time: " + i);
+              let fr = new content.window.FileReader();
+              fr.readAsText(e.data);
+              fr.onerror = () => {
+                ok(false, "Something wrong happened.");
+              };
+
+              fr.onloadend = () => {
+                is(fr.result.length, e.data.size, "FileReader worked fine.");
+                if (!--count) {
+                  resolve(true);
+                }
+              };
+            }
+          });
+        }
+
+        let promises = [];
+        for (let i = 0; i < 5; ++i) {
+          promises.push(realTest());
+        }
+
+        Promise.all(promises).then(() => {
+          resolve(true);
+        });
+      };
+    });
+  });
+
+  let status = await SpecialPowers.spawn(browser1, [], function() {
+    let p = new content.window.Promise(resolve => {
+      let xhr = new content.window.XMLHttpRequest();
+      xhr.open("GET", "temporary.sjs", true);
+      xhr.responseType = "blob";
+      xhr.onload = () => {
+        resolve(xhr.response);
+      };
+      xhr.send();
+    });
+
+    return p.then(blob => {
+      function realTest() {
+        return new content.window.Promise(resolve => {
+          info("Let's broadcast the blob...");
+          let bc = new content.window.BroadcastChannel("foobar");
+          bc.postMessage(blob);
+
+          info("Here the test...");
+          let count = 10;
+          for (let i = 0; i < count; ++i) {
+            info("FileReader at the same time: " + i);
+            let fr = new content.window.FileReader();
+            fr.readAsText(blob);
+            fr.onerror = () => {
+              ok(false, "Something wrong happened.");
+            };
+
+            fr.onloadend = () => {
+              is(fr.result.length, blob.size, "FileReader worked fine.");
+              if (!--count) {
+                resolve(true);
+              }
+            };
+          }
+        });
+      }
+
+      let promises = [];
+      for (let i = 0; i < 5; ++i) {
+        promises.push(realTest());
+      }
+
+      return Promise.all(promises);
+    });
+  });
+
+  ok(status, "All good for tab1!");
+
+  status = await SpecialPowers.spawn(browser2, [], function() {
+    return content.window.testPromise;
+  });
+
+  ok(status, "All good for tab2!");
+
+  BrowserTestUtils.removeTab(tab1);
+  BrowserTestUtils.removeTab(tab2);
+});
diff --git a/dom/file/ipc/tests/empty.html b/dom/file/ipc/tests/empty.html
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/dom/file/ipc/tests/empty.html
diff --git a/dom/file/ipc/tests/green.jpg b/dom/file/ipc/tests/green.jpg
new file mode 100644
index 0000000000..48c454d27c
--- /dev/null
+++ b/dom/file/ipc/tests/green.jpg
diff --git a/dom/file/ipc/tests/mochitest.ini b/dom/file/ipc/tests/mochitest.ini
new file mode 100644
index 0000000000..75bda265fb
--- /dev/null
+++ b/dom/file/ipc/tests/mochitest.ini
@@ -0,0 +1,10 @@
+[DEFAULT]
+support-files = script_file.js
+
+[test_ipcBlob_fileReaderSync.html]
+[test_ipcBlob_workers.html]
+[test_ipcBlob_createImageBitmap.html]
+support-files = green.jpg
+[test_ipcBlob_emptyMultiplex.html]
+[test_ipcBlob_mixedMultiplex.html]
+support-files = ok.sjs
diff --git a/dom/file/ipc/tests/ok.sjs b/dom/file/ipc/tests/ok.sjs
new file mode 100644
index 0000000000..42f65733d9
--- /dev/null
+++ b/dom/file/ipc/tests/ok.sjs
@@ -0,0 +1,11 @@
+const CC = Components.Constructor;
+const BinaryInputStream = CC(
+  "@mozilla.org/binaryinputstream;1",
+  "nsIBinaryInputStream",
+  "setInputStream"
+);
+
+function handleRequest(request, response) {
+  response.setHeader("Content-Type", "text/html", false);
+  response.write(request.getHeader("Content-Length"));
+}
diff --git a/dom/file/ipc/tests/script_file.js b/dom/file/ipc/tests/script_file.js
new file mode 100644
index 0000000000..0f4e9665be
--- /dev/null
+++ b/dom/file/ipc/tests/script_file.js
@@ -0,0 +1,53 @@
+/* eslint-env mozilla/chrome-script */
+
+Cu.importGlobalProperties(["File"]);
+
+addMessageListener("file.open", function(e) {
+  var testFile = Cc["@mozilla.org/file/directory_service;1"]
+    .getService(Ci.nsIDirectoryService)
+    .QueryInterface(Ci.nsIProperties)
+    .get("ProfD", Ci.nsIFile);
+  testFile.append("ipc_fileReader_testing");
+  testFile.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, 0o600);
+
+  var outStream = Cc[
+    "@mozilla.org/network/file-output-stream;1"
+  ].createInstance(Ci.nsIFileOutputStream);
+  outStream.init(
+    testFile,
+    0x02 | 0x08 | 0x20, // write, create, truncate
+    0o666,
+    0
+  );
+
+  var fileData = "Hello World!";
+  outStream.write(fileData, fileData.length);
+  outStream.close();
+
+  File.createFromNsIFile(testFile).then(function(file) {
+    sendAsyncMessage("file.opened", { file });
+  });
+});
+
+addMessageListener("emptyfile.open", function(e) {
+  var testFile = Cc["@mozilla.org/file/directory_service;1"]
+    .getService(Ci.nsIDirectoryService)
+    .QueryInterface(Ci.nsIProperties)
+    .get("ProfD", Ci.nsIFile);
+  testFile.append("ipc_fileReader_testing");
+  testFile.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, 0o600);
+
+  var outStream = Cc[
+    "@mozilla.org/network/file-output-stream;1"
+  ].createInstance(Ci.nsIFileOutputStream);
+  outStream.init(
+    testFile,
+    0x02 | 0x08 | 0x20, // write, create, truncate
+    0o666,
+    0
+  );
+
+  File.createFromNsIFile(testFile).then(function(file) {
+    sendAsyncMessage("emptyfile.opened", { file });
+  });
+});
diff --git a/dom/file/ipc/tests/temporary.sjs b/dom/file/ipc/tests/temporary.sjs
new file mode 100644
index 0000000000..76db4e2f2e
--- /dev/null
+++ b/dom/file/ipc/tests/temporary.sjs
@@ -0,0 +1,6 @@
+function handleRequest(request, response) {
+  response.setHeader("Content-Type", "text/plain", false);
+
+  var data = new Array(1024 * 64).join("1234567890ABCDEF");
+  response.bodyOutputStream.write(data, data.length);
+}
diff --git a/dom/file/ipc/tests/test_ipcBlob_createImageBitmap.html b/dom/file/ipc/tests/test_ipcBlob_createImageBitmap.html
new file mode 100644
index 0000000000..868888c529
--- /dev/null
+++ b/dom/file/ipc/tests/test_ipcBlob_createImageBitmap.html
@@ -0,0 +1,84 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test IPCBlob and CreateImageBitmap</title>
+  <script type="text/javascript" src="/MochiKit/MochiKit.js"></script>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<script type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+
+function test_mainThread() {
+  let bc = new BroadcastChannel('testMainThread');
+  bc.onmessage = e => {
+    createImageBitmap(e.data).then(image => {
+      ok(image.height, "this image has a valid size.");
+    }, () => {
+      ok(false, "error creating the image!");
+    }).then(next);
+  }
+
+  fetch('green.jpg').then(r => r.blob()).then(blob => {
+    let bc = new BroadcastChannel('testMainThread');
+    bc.postMessage(blob);
+  });
+}
+
+function test_worker() {
+  function workerScript() {
+    function ok(a, msg) { postMessage({ type: 'test', status: !!a, msg }); };
+    function finish() { postMessage({ type: 'finish' }); };
+
+    let bc = new BroadcastChannel('testWorker');
+    bc.onmessage = e => {
+      createImageBitmap(e.data).then(image => {
+        ok(image.height, "this image has a valid size.");
+      }, () => {
+        ok(false, "error creating the image!");
+      }).then(finish);
+    }
+
+    fetch('http://mochi.test:8888/tests/dom/file/ipc/tests/green.jpg').then(r => r.blob()).then(blob => {
+      let bc = new BroadcastChannel('testWorker');
+      bc.postMessage(blob);
+    });
+  }
+  let workerUrl = URL.createObjectURL(new Blob(["(", workerScript.toString(), ")()"]));
+  let worker = new Worker(workerUrl);
+
+  worker.onmessage = event => {
+    if (event.data.type == 'test') {
+      ok(event.data.status, event.data.msg);
+      return;
+    }
+
+    if (event.data.type == 'finish') {
+      next();
+    }
+  }
+}
+
+let tests = [
+  test_mainThread,
+  test_worker,
+];
+
+function next() {
+  if (!tests.length) {
+    SimpleTest.finish();
+    return;
+  }
+
+  let test = tests.shift();
+  test();
+}
+
+next();
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/file/ipc/tests/test_ipcBlob_emptyMultiplex.html b/dom/file/ipc/tests/test_ipcBlob_emptyMultiplex.html
new file mode 100644
index 0000000000..0487069467
--- /dev/null
+++ b/dom/file/ipc/tests/test_ipcBlob_emptyMultiplex.html
@@ -0,0 +1,45 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test an empty IPCBlob together with other parts</title>
+  <script type="text/javascript" src="/MochiKit/MochiKit.js"></script>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<script type="text/javascript">
+
+function checkContent(msg, content) {
+  return new Promise(resolve => {
+    let fr = new FileReader();
+    fr.readAsText(new Blob(content));
+    fr.onloadend = () => {
+      is(fr.result, "Hello world!", "The content matches: " + msg);
+      resolve();
+    };
+  });
+}
+
+SimpleTest.waitForExplicitFinish();
+
+let url = SimpleTest.getTestFileURL("script_file.js");
+
+let script = SpecialPowers.loadChromeScript(url);
+script.addMessageListener("emptyfile.opened", message => {
+  checkContent("middle", ["Hello ", message.file, "world!"]).
+  then(() => checkContent("begin", [message.file, "Hello world!"])).
+  then(() => checkContent("end", ["Hello world!", message.file])).
+  then(() => checkContent("random", [message.file, message.file, "Hello world!", message.file])).
+  then(() => checkContent("random 2", [message.file, message.file, "Hello ",
+                                       message.file, "world", message.file,
+                                       message.file, "!", message.file, "",
+                                       message.file, message.file])).
+  then(SimpleTest.finish);
+});
+
+script.sendAsyncMessage("emptyfile.open");
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/file/ipc/tests/test_ipcBlob_fileReaderSync.html b/dom/file/ipc/tests/test_ipcBlob_fileReaderSync.html
new file mode 100644
index 0000000000..f37d4b79ed
--- /dev/null
+++ b/dom/file/ipc/tests/test_ipcBlob_fileReaderSync.html
@@ -0,0 +1,100 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test IPCBlob and FileReaderSync</title>
+  <script type="text/javascript" src="/MochiKit/MochiKit.js"></script>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<script type="text/javascript">
+
+function workerScript() {
+  onmessage = function(event) {
+    let readerMemoryBlob = new FileReaderSync();
+    let status = readerMemoryBlob.readAsText(new Blob(['hello world'])) == 'hello world';
+    postMessage({ status, message: "FileReaderSync with memory blob still works" });
+
+    let readerIPCBlob1 = new FileReaderSync();
+    postMessage({ blob: event.data, method: 'readAsText',
+                  data: readerIPCBlob1.readAsText(event.data)});
+
+    let readerIPCBlob2 = new FileReaderSync();
+    postMessage({ blob: event.data, method: 'readAsArrayBuffer',
+                  data: readerIPCBlob2.readAsArrayBuffer(event.data)});
+
+    let readerIPCBlob3 = new FileReaderSync();
+    postMessage({ blob: event.data, method: 'readAsDataURL',
+                  data: readerIPCBlob3.readAsDataURL(event.data)});
+
+    let multipartBlob = new Blob(['wow', event.data]);
+
+    let readerIPCBlobMultipart1 = new FileReaderSync();
+    postMessage({ blob: multipartBlob, method: 'readAsText',
+                  data: readerIPCBlobMultipart1.readAsText(multipartBlob)});
+
+    let readerIPCBlobMultipart2 = new FileReaderSync();
+    postMessage({ blob: multipartBlob, method: 'readAsArrayBuffer',
+                  data: readerIPCBlobMultipart2.readAsArrayBuffer(multipartBlob)});
+
+    let readerIPCBlobMultipart3 = new FileReaderSync();
+    postMessage({ blob: multipartBlob, method: 'readAsDataURL',
+                  data: readerIPCBlobMultipart3.readAsDataURL(multipartBlob)});
+
+    postMessage({ finish: true });
+  }
+}
+
+let completed = false;
+let pendingTasks = 0;
+function maybeFinish() {
+  if (completed && !pendingTasks) {
+    SimpleTest.finish();
+  }
+}
+
+let workerUrl = URL.createObjectURL(new Blob(["(", workerScript.toString(), ")()"]));
+let worker = new Worker(workerUrl);
+worker.onmessage = event => {
+  if ("status" in event.data) {
+    ok(event.data.status, event.data.message);
+    return;
+  }
+
+  if ("blob" in event.data) {
+    let fr = new FileReader();
+    fr[event.data.method](event.data.blob);
+    ++pendingTasks;
+    fr.onload = () => {
+      if (event.data.method != 'readAsArrayBuffer') {
+        is(event.data.data, fr.result, "The file has been read");
+      } else {
+        is(event.data.data.byteLength, fr.result.byteLength, "The file has been read");
+      }
+      --pendingTasks;
+      maybeFinish();
+    }
+
+    return;
+  }
+
+  if ("finish" in event.data) {
+    completed = true;
+    maybeFinish();
+  }
+};
+
+let url = SimpleTest.getTestFileURL("script_file.js");
+let script = SpecialPowers.loadChromeScript(url);
+script.addMessageListener("file.opened", message => {
+  worker.postMessage(message.file);
+});
+
+script.sendAsyncMessage("file.open");
+
+SimpleTest.waitForExplicitFinish();
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/file/ipc/tests/test_ipcBlob_mixedMultiplex.html b/dom/file/ipc/tests/test_ipcBlob_mixedMultiplex.html
new file mode 100644
index 0000000000..c8e046fa88
--- /dev/null
+++ b/dom/file/ipc/tests/test_ipcBlob_mixedMultiplex.html
@@ -0,0 +1,41 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test an empty IPCBlob together with other parts</title>
+  <script type="text/javascript" src="/MochiKit/MochiKit.js"></script>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<script type="text/javascript">
+
+let url = SimpleTest.getTestFileURL("script_file.js");
+let data = new Array(1024*1024).join('A');
+
+let script = SpecialPowers.loadChromeScript(url);
+script.addMessageListener("file.opened", message => {
+  let blob = new Blob([data]);
+
+  let form = new FormData();
+  form.append("blob1", blob);
+  form.append("blob2", message.file);
+  form.append("blob3", blob);
+
+  fetch("ok.sjs", {
+    method: "POST",
+    body: form,
+  })
+  .then(r => r.text())
+  .then(r => {
+    ok(parseInt(r, 10) > (data.length * 2), "We have data");
+  })
+  . then(SimpleTest.finish);
+});
+
+script.sendAsyncMessage("file.open");
+SimpleTest.waitForExplicitFinish();
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/file/ipc/tests/test_ipcBlob_workers.html b/dom/file/ipc/tests/test_ipcBlob_workers.html
new file mode 100644
index 0000000000..a473948f25
--- /dev/null
+++ b/dom/file/ipc/tests/test_ipcBlob_workers.html
@@ -0,0 +1,121 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test IPCBlob and Workers</title>
+  <script type="text/javascript" src="/MochiKit/MochiKit.js"></script>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<script type="text/javascript">
+
+function test_workerOwner() {
+  info("test_workerOwner");
+
+  function workerScript() {
+    onmessage = e => {
+      e.ports[0].onmessage = event => {
+        let reader = new FileReader();
+        reader.readAsText(event.data);
+        reader.onloadend = () => {
+          let status = reader.result == 'hello world';
+          postMessage(status);
+        }
+      }
+    }
+  }
+
+  let mc = new MessageChannel();
+  mc.port1.postMessage(new Blob(['hello world']));
+
+  let workerUrl = URL.createObjectURL(new Blob(["(", workerScript.toString(), ")()"]));
+  let worker = new Worker(workerUrl);
+
+  worker.postMessage("", [mc.port2]);
+  worker.onmessage = event => {
+    ok(event.data, "All is done!");
+    next();
+  }
+}
+
+function test_workerToMainThread() {
+  info("test_workerToMainThread");
+  function workerScript() {
+    onmessage = e => {
+      e.ports[0].onmessage = event => {
+        postMessage(event.data);
+      }
+    }
+  }
+
+  let mc = new MessageChannel();
+  mc.port1.postMessage(new Blob(['hello world']));
+
+  let workerUrl = URL.createObjectURL(new Blob(["(", workerScript.toString(), ")()"]));
+  let worker = new Worker(workerUrl);
+
+  worker.postMessage("", [mc.port2]);
+  worker.onmessage = event => {
+    info("Blob received back, terminate the worker and force GC");
+    worker.terminate();
+    worker = null;
+    SpecialPowers.forceGC();
+
+    var fr = new FileReader();
+    fr.readAsText(event.data);
+    fr.onloadend = () => {
+      is(fr.result, "hello world", "Data matches");
+      next();
+    }
+  }
+}
+
+function test_workerOwnerPlusFileReaderSync() {
+  info("test_workerOwnerPlusFileReaderSync");
+
+  function workerScript() {
+    onmessage = e => {
+      e.ports[0].onmessage = event => {
+        let reader = new FileReaderSync();
+        let status = reader.readAsText(event.data) == 'hello world';
+         postMessage(status);
+      }
+    }
+  }
+
+  let mc = new MessageChannel();
+  mc.port1.postMessage(new Blob(['hello world']));
+
+  let workerUrl = URL.createObjectURL(new Blob(["(", workerScript.toString(), ")()"]));
+  let worker = new Worker(workerUrl);
+
+  worker.postMessage("", [mc.port2]);
+  worker.onmessage = event => {
+    ok(event.data, "All is done!");
+    next();
+  }
+}
+
+var tests = [
+  test_workerOwner,
+  test_workerToMainThread,
+  test_workerOwnerPlusFileReaderSync,
+];
+
+function next() {
+  if (!tests.length) {
+    SimpleTest.finish();
+    return;
+  }
+
+  var test = tests.shift();
+  test();
+}
+
+SimpleTest.waitForExplicitFinish();
+next();
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/file/moz.build b/dom/file/moz.build
new file mode 100644
index 0000000000..2a5831454b
--- /dev/null
+++ b/dom/file/moz.build
@@ -0,0 +1,62 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+with Files("**"):
+    BUG_COMPONENT = ("Core", "DOM: File")
+
+DIRS += ["ipc", "uri"]
+
+EXPORTS.mozilla.dom += [
+    "BaseBlobImpl.h",
+    "Blob.h",
+    "BlobImpl.h",
+    "BlobSet.h",
+    "EmptyBlobImpl.h",
+    "File.h",
+    "FileBlobImpl.h",
+    "FileCreatorHelper.h",
+    "FileList.h",
+    "FileReader.h",
+    "FileReaderSync.h",
+    "MemoryBlobImpl.h",
+    "MultipartBlobImpl.h",
+    "MutableBlobStorage.h",
+    "MutableBlobStreamListener.h",
+    "StreamBlobImpl.h",
+]
+
+UNIFIED_SOURCES += [
+    "BaseBlobImpl.cpp",
+    "Blob.cpp",
+    "BlobImpl.cpp",
+    "BlobSet.cpp",
+    "EmptyBlobImpl.cpp",
+    "File.cpp",
+    "FileBlobImpl.cpp",
+    "FileCreatorHelper.cpp",
+    "FileList.cpp",
+    "FileReader.cpp",
+    "FileReaderSync.cpp",
+    "MemoryBlobImpl.cpp",
+    "MultipartBlobImpl.cpp",
+    "MutableBlobStorage.cpp",
+    "MutableBlobStreamListener.cpp",
+    "StreamBlobImpl.cpp",
+    "StringBlobImpl.cpp",
+    "TemporaryFileBlobImpl.cpp",
+]
+
+LOCAL_INCLUDES += [
+    "/dom/file/ipc",
+]
+
+MOCHITEST_MANIFESTS += ["tests/mochitest.ini"]
+
+XPCSHELL_TESTS_MANIFESTS += ["tests/xpcshell.ini"]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"
diff --git a/dom/file/tests/common_blob.js b/dom/file/tests/common_blob.js
new file mode 100644
index 0000000000..98a4cde743
--- /dev/null
+++ b/dom/file/tests/common_blob.js
@@ -0,0 +1,395 @@
+const RANGE_1 = 1;
+const RANGE_2 = 2;
+
+function testBlob(file, contents, testName) {
+  // Load file using FileReader
+  return (
+    new Promise(resolve => {
+      let r = new FileReader();
+      r.onload = event => {
+        is(
+          event.target.readyState,
+          FileReader.DONE,
+          "[FileReader] readyState in test FileReader.readAsBinaryString of " +
+            testName
+        );
+        is(
+          event.target.error,
+          null,
+          "[FileReader] no error in test FileReader.readAsBinaryString of " +
+            testName
+        );
+        // Do not use |is(event.target.result, contents, "...");| that may output raw binary data.
+        is(
+          event.target.result.length,
+          contents.length,
+          "[FileReader] Length of result in test FileReader.readAsBinaryString of " +
+            testName
+        );
+        ok(
+          event.target.result == contents,
+          "[FileReader] Content of result in test FileReader.readAsBinaryString of " +
+            testName
+        );
+        is(
+          event.lengthComputable,
+          true,
+          "[FileReader] lengthComputable in test FileReader.readAsBinaryString of " +
+            testName
+        );
+        is(
+          event.loaded,
+          contents.length,
+          "[FileReader] Loaded length in test FileReader.readAsBinaryString of " +
+            testName
+        );
+        is(
+          event.total,
+          contents.length,
+          "[FileReader] Total length in test FileReader.readAsBinaryString of " +
+            testName
+        );
+        resolve();
+      };
+      r.readAsBinaryString(file);
+    })
+
+      // Load file using URL.createObjectURL and XMLHttpRequest
+      .then(() => {
+        return new Promise(resolve => {
+          let xhr = new XMLHttpRequest();
+          xhr.open("GET", URL.createObjectURL(file));
+          xhr.onload = event => {
+            XHRLoadHandler(
+              event,
+              resolve,
+              contents,
+              "XMLHttpRequest load of " + testName
+            );
+          };
+          xhr.overrideMimeType("text/plain; charset=x-user-defined");
+          xhr.send();
+        });
+      })
+
+      // Send file to server using FormData and XMLHttpRequest
+      .then(() => {
+        return new Promise(resolve => {
+          let xhr = new XMLHttpRequest();
+          xhr.onload = function(event) {
+            checkMPSubmission(JSON.parse(event.target.responseText), [
+              { name: "hello", value: "world" },
+              {
+                name: "myfile",
+                value: contents,
+                fileName: file.name || "blob",
+                contentType: file.type || "application/octet-stream",
+              },
+            ]);
+            resolve();
+          };
+          xhr.open("POST", "../../../dom/html/test/form_submit_server.sjs");
+
+          let fd = new FormData();
+          fd.append("hello", "world");
+          fd.append("myfile", file);
+
+          xhr.send(fd);
+        });
+      })
+
+      // Send file to server using plain XMLHttpRequest
+      .then(() => {
+        return new Promise(resolve => {
+          let xhr = new XMLHttpRequest();
+          xhr.open("POST", "../../../dom/xhr/tests/file_XHRSendData.sjs");
+
+          xhr.onload = function(event) {
+            is(
+              event.target.getResponseHeader("Result-Content-Type"),
+              file.type ? file.type : null,
+              "request content-type in XMLHttpRequest send of " + testName
+            );
+            is(
+              event.target.getResponseHeader("Result-Content-Length"),
+              String(file.size),
+              "request content-length in XMLHttpRequest send of " + testName
+            );
+          };
+
+          xhr.addEventListener("load", event => {
+            XHRLoadHandler(
+              event,
+              resolve,
+              contents,
+              "XMLHttpRequest send of " + testName
+            );
+          });
+          xhr.overrideMimeType("text/plain; charset=x-user-defined");
+          xhr.send(file);
+        });
+      })
+  );
+}
+
+function testSlice(file, size, type, contents, fileType, range) {
+  is(file.type, type, fileType + " file is correct type");
+  is(file.size, size, fileType + " file is correct size");
+  if (fileType == "fileFile") {
+    ok(file instanceof File, fileType + " file is a File");
+  } else if (fileType == "memFile") {
+    ok(!(file instanceof File), fileType + " file is not a File");
+  }
+  ok(file instanceof Blob, fileType + " file is also a Blob");
+
+  let slice = file.slice(0, size);
+  ok(slice instanceof Blob, fileType + " fullsize slice is a Blob");
+  ok(!(slice instanceof File), fileType + " fullsize slice is not a File");
+
+  slice = file.slice(0, 1234);
+  ok(slice instanceof Blob, fileType + " sized slice is a Blob");
+  ok(!(slice instanceof File), fileType + " sized slice is not a File");
+
+  slice = file.slice(0, size, "foo/bar");
+  is(slice.type, "foo/bar", fileType + " fullsize slice foo/bar type");
+
+  slice = file.slice(0, 5432, "foo/bar");
+  is(slice.type, "foo/bar", fileType + " sized slice foo/bar type");
+
+  is(slice.slice(0, 10).type, "", fileType + " slice-slice type");
+  is(slice.slice(0, 10).size, 10, fileType + " slice-slice size");
+  is(
+    slice.slice(0, 10, "hello/world").type,
+    "hello/world",
+    fileType + " slice-slice hello/world type"
+  );
+  is(
+    slice.slice(0, 10, "hello/world").size,
+    10,
+    fileType + " slice-slice hello/world size"
+  );
+
+  // Start, end, expected size
+  var indexes_range_1 = [
+    [0, size, size],
+    [0, 1234, 1234],
+    [size - 500, size, 500],
+    [size - 500, size + 500, 500],
+    [size + 500, size + 1500, 0],
+    [0, 0, 0],
+    [1000, 1000, 0],
+    [size, size, 0],
+    [undefined, undefined, size],
+    [0, undefined, size],
+  ];
+
+  var indexes_range_2 = [
+    [100, undefined, size - 100],
+    [-100, undefined, 100],
+    [100, -100, size - 200],
+    [-size - 100, undefined, size],
+    [-2 * size - 100, 500, 500],
+    [0, -size - 100, 0],
+    [100, -size - 100, 0],
+    [50, -size + 100, 50],
+    [0, 33000, 33000],
+    [1000, 34000, 33000],
+  ];
+
+  let indexes;
+  if (range == RANGE_1) {
+    indexes = indexes_range_1;
+  } else if (range == RANGE_2) {
+    indexes = indexes_range_2;
+  } else {
+    throw "Invalid range!";
+  }
+
+  function runNextTest() {
+    if (!indexes.length) {
+      return Promise.resolve(true);
+    }
+
+    let index = indexes.shift();
+
+    let sliceContents;
+    let testName;
+    if (index[0] == undefined) {
+      slice = file.slice();
+      sliceContents = contents.slice();
+      testName = fileType + " slice()";
+    } else if (index[1] == undefined) {
+      slice = file.slice(index[0]);
+      sliceContents = contents.slice(index[0]);
+      testName = fileType + " slice(" + index[0] + ")";
+    } else {
+      slice = file.slice(index[0], index[1]);
+      sliceContents = contents.slice(index[0], index[1]);
+      testName = fileType + " slice(" + index[0] + ", " + index[1] + ")";
+    }
+
+    is(slice.type, "", testName + " type");
+    is(slice.size, index[2], testName + " size");
+    is(sliceContents.length, index[2], testName + " data size");
+
+    return testBlob(slice, sliceContents, testName).then(runNextTest);
+  }
+
+  return runNextTest()
+    .then(() => {
+      // Slice of slice
+      let sliceOfSlice = file.slice(0, 40000);
+      return testBlob(
+        sliceOfSlice.slice(5000, 42000),
+        contents.slice(5000, 40000),
+        "file slice slice"
+      );
+    })
+    .then(() => {
+      // ...of slice of slice
+      let sliceOfSlice = file
+        .slice(0, 40000)
+        .slice(5000, 42000)
+        .slice(400, 700);
+      SpecialPowers.gc();
+      return testBlob(
+        sliceOfSlice,
+        contents.slice(5400, 5700),
+        "file slice slice slice"
+      );
+    });
+}
+
+function convertXHRBinary(s) {
+  let res = "";
+  for (let i = 0; i < s.length; ++i) {
+    res += String.fromCharCode(s.charCodeAt(i) & 255);
+  }
+  return res;
+}
+
+function XHRLoadHandler(event, resolve, contents, testName) {
+  is(event.target.readyState, 4, "[XHR] readyState in test " + testName);
+  is(event.target.status, 200, "[XHR] no error in test " + testName);
+  // Do not use |is(convertXHRBinary(event.target.responseText), contents, "...");| that may output raw binary data.
+  let convertedData = convertXHRBinary(event.target.responseText);
+  is(
+    convertedData.length,
+    contents.length,
+    "[XHR] Length of result in test " + testName
+  );
+  ok(convertedData == contents, "[XHR] Content of result in test " + testName);
+  is(
+    event.lengthComputable,
+    event.total != 0,
+    "[XHR] lengthComputable in test " + testName
+  );
+  is(event.loaded, contents.length, "[XHR] Loaded length in test " + testName);
+  is(event.total, contents.length, "[XHR] Total length in test " + testName);
+  resolve();
+}
+
+function checkMPSubmission(sub, expected) {
+  function getPropCount(o) {
+    let x,
+      l = 0;
+    for (x in o) {
+      ++l;
+    }
+    return l;
+  }
+
+  is(sub.length, expected.length, "Correct number of items");
+  let i;
+  for (i = 0; i < expected.length; ++i) {
+    if (!("fileName" in expected[i])) {
+      is(
+        sub[i].headers["Content-Disposition"],
+        'form-data; name="' + expected[i].name + '"',
+        "Correct name (A)"
+      );
+      is(getPropCount(sub[i].headers), 1, "Wrong number of headers (A)");
+    } else {
+      is(
+        sub[i].headers["Content-Disposition"],
+        'form-data; name="' +
+          expected[i].name +
+          '"; filename="' +
+          expected[i].fileName +
+          '"',
+        "Correct name (B)"
+      );
+      is(
+        sub[i].headers["Content-Type"],
+        expected[i].contentType,
+        "Correct content type (B)"
+      );
+      is(getPropCount(sub[i].headers), 2, "Wrong number of headers (B)");
+    }
+    // Do not use |is(sub[i].body, expected[i].value, "...");| that may output raw binary data.
+    is(sub[i].body.length, expected[i].value.length, "Length of correct value");
+    ok(sub[i].body == expected[i].value, "Content of correct value");
+  }
+}
+
+function createCanvasURL() {
+  return new Promise(resolve => {
+    // Create a decent-sized image
+    let cx = $("canvas").getContext("2d");
+    let s = cx.canvas.width;
+    let grad = cx.createLinearGradient(0, 0, s - 1, s - 1);
+    for (i = 0; i < 0.95; i += 0.1) {
+      grad.addColorStop(i, "white");
+      grad.addColorStop(i + 0.05, "black");
+    }
+    grad.addColorStop(1, "white");
+    cx.fillStyle = grad;
+    cx.fillRect(0, 0, s - 1, s - 1);
+    cx.fillStyle = "rgba(200, 0, 0, 0.9)";
+    cx.fillRect(0.1 * s, 0.1 * s, 0.7 * s, 0.7 * s);
+    cx.strokeStyle = "rgba(0, 0, 130, 0.5)";
+    cx.lineWidth = 0.14 * s;
+    cx.beginPath();
+    cx.arc(0.6 * s, 0.6 * s, 0.3 * s, 0, Math.PI * 2, true);
+    cx.stroke();
+    cx.closePath();
+    cx.fillStyle = "rgb(0, 255, 0)";
+    cx.beginPath();
+    cx.arc(0.1 * s, 0.8 * s, 0.1 * s, 0, Math.PI * 2, true);
+    cx.fill();
+    cx.closePath();
+
+    let data = atob(
+      cx.canvas
+        .toDataURL("image/png")
+        .substring("data:text/png;base64,".length + 1)
+    );
+
+    // This might fail if we dramatically improve the png encoder. If that happens
+    // please increase the complexity or size of the image generated above to ensure
+    // that we're testing with files that are large enough.
+    ok(data.length > 65536, "test data sufficiently large");
+
+    resolve(data);
+  });
+}
+
+function createFile(data, name) {
+  return new Promise(resolve => {
+    SpecialPowers.createFiles([{ name, data }], files => {
+      resolve(files[0]);
+    });
+  });
+}
+
+function toBlobPromise(canvas) {
+  function BlobListener(callback, file) {
+    var reader = new FileReader();
+    reader.onload = () => callback(file);
+    reader.readAsDataURL(file);
+  }
+
+  return new Promise(resolve => {
+    canvas.toBlob(BlobListener.bind(undefined, resolve));
+  });
+}
diff --git a/dom/file/tests/common_blob_reading.js b/dom/file/tests/common_blob_reading.js
new file mode 100644
index 0000000000..776ffececf
--- /dev/null
+++ b/dom/file/tests/common_blob_reading.js
@@ -0,0 +1,50 @@
+async function testBlobText(blob, content) {
+  let text = await blob.text();
+  is(text, content, "blob.text()");
+}
+
+async function testBlobArrayBuffer(blob, content) {
+  let ab = await blob.arrayBuffer();
+  is(ab.byteLength, content.length, "blob.arrayBuffer()");
+}
+
+async function testBlobStream(blob, content) {
+  let s = await blob.stream();
+  ok(s instanceof ReadableStream, "We have a ReadableStream");
+
+  let data = await s.getReader().read();
+  ok(!data.done, "Nothing is done yet");
+  for (let i = 0; i < data.value.length; ++i) {
+    is(String.fromCharCode(data.value[i]), content[i], "blob.stream() - " + i);
+  }
+}
+
+function workify(func, blob, content) {
+  info("Workifying " + func);
+
+  return new Promise((resolve, reject) => {
+    let worker = new Worker("worker_blob_reading.js");
+    worker.postMessage({ func, blob, content });
+    worker.onmessage = function(e) {
+      if (e.data.type == "done") {
+        resolve();
+        return;
+      }
+
+      if (e.data.type == "error") {
+        reject(e.data.message);
+        return;
+      }
+
+      if (e.data.type == "test") {
+        ok(e.data.test, e.data.message);
+        return;
+      }
+
+      if (e.data.type == "info") {
+        info(e.data.message);
+        return;
+      }
+    };
+  });
+}
diff --git a/dom/file/tests/common_blob_types.js b/dom/file/tests/common_blob_types.js
new file mode 100644
index 0000000000..95501e58e5
--- /dev/null
+++ b/dom/file/tests/common_blob_types.js
@@ -0,0 +1,82 @@
+let blobTypes = [
+  {
+    type: "memory",
+    factory: async content => {
+      return new Blob([content]);
+    },
+    blobImplType: "MultipartBlobImpl[StringBlobImpl]",
+  },
+
+  {
+    type: "ipcBlob",
+    factory: async content => {
+      return new Promise(resolve => {
+        let bc1 = new BroadcastChannel("blob tests");
+        bc1.onmessage = e => {
+          resolve(e.data);
+        };
+
+        let bc2 = new BroadcastChannel("blob tests");
+        bc2.postMessage(new Blob([content]));
+      });
+    },
+    blobImplType:
+      "StreamBlobImpl[StreamBlobImpl[MultipartBlobImpl[StringBlobImpl]]]",
+  },
+
+  {
+    type: "memoryBlob",
+    factory: async content => {
+      return new Promise(resolve => {
+        var xhr = new XMLHttpRequest();
+        xhr.open(
+          "POST",
+          "http://mochi.test:8888/browser/dom/xhr/tests/temporaryFileBlob.sjs"
+        );
+        xhr.responseType = "blob";
+        xhr.send(content);
+        xhr.onloadend = _ => {
+          resolve(xhr.response);
+        };
+      });
+    },
+    blobImplType: "MemoryBlobImpl",
+  },
+
+  {
+    type: "temporaryBlob",
+    factory: async content => {
+      await SpecialPowers.pushPrefEnv({
+        set: [["dom.blob.memoryToTemporaryFile", 1]],
+      });
+
+      return new Promise(resolve => {
+        var xhr = new XMLHttpRequest();
+        xhr.open(
+          "POST",
+          "http://mochi.test:8888/browser/dom/xhr/tests/temporaryFileBlob.sjs"
+        );
+        xhr.responseType = "blob";
+        xhr.send(content);
+        xhr.onloadend = _ => {
+          resolve(xhr.response);
+        };
+      });
+    },
+    blobImplType: "StreamBlobImpl[TemporaryFileBlobImpl]",
+  },
+];
+
+async function forEachBlobType(content, cb) {
+  for (let i = 0; i < blobTypes.length; ++i) {
+    info("Running tests for " + blobTypes[i].type);
+    let blob = await blobTypes[i].factory(content);
+    is(
+      SpecialPowers.wrap(blob).blobImplType,
+      blobTypes[i].blobImplType,
+      "Correct blobImplType"
+    );
+    ok(blob instanceof Blob, "Blob created");
+    await cb(blob, content);
+  }
+}
diff --git a/dom/file/tests/common_fileReader.js b/dom/file/tests/common_fileReader.js
new file mode 100644
index 0000000000..3df3a36114
--- /dev/null
+++ b/dom/file/tests/common_fileReader.js
@@ -0,0 +1,848 @@
+function test_setup() {
+  return new Promise(resolve => {
+    const minFileSize = 20000;
+
+    // Create strings containing data we'll test with. We'll want long
+    // strings to ensure they span multiple buffers while loading
+    let testTextData = "asd b\tlah\u1234w\u00a0r";
+    while (testTextData.length < minFileSize) {
+      testTextData = testTextData + testTextData;
+    }
+
+    let testASCIIData = "abcdef 123456\n";
+    while (testASCIIData.length < minFileSize) {
+      testASCIIData = testASCIIData + testASCIIData;
+    }
+
+    let testBinaryData = "";
+    for (let i = 0; i < 256; i++) {
+      testBinaryData += String.fromCharCode(i);
+    }
+    while (testBinaryData.length < minFileSize) {
+      testBinaryData = testBinaryData + testBinaryData;
+    }
+
+    let dataurldata0 = testBinaryData.substr(
+      0,
+      testBinaryData.length - (testBinaryData.length % 3)
+    );
+    let dataurldata1 = testBinaryData.substr(
+      0,
+      testBinaryData.length - 2 - (testBinaryData.length % 3)
+    );
+    let dataurldata2 = testBinaryData.substr(
+      0,
+      testBinaryData.length - 1 - (testBinaryData.length % 3)
+    );
+
+    //Set up files for testing
+    let openerURL = SimpleTest.getTestFileURL("fileapi_chromeScript.js");
+    let opener = SpecialPowers.loadChromeScript(openerURL);
+
+    opener.addMessageListener("files.opened", message => {
+      let [
+        asciiFile,
+        binaryFile,
+        nonExistingFile,
+        utf8TextFile,
+        utf16TextFile,
+        emptyFile,
+        dataUrlFile0,
+        dataUrlFile1,
+        dataUrlFile2,
+      ] = message;
+
+      resolve({
+        blobs: {
+          asciiFile,
+          binaryFile,
+          nonExistingFile,
+          utf8TextFile,
+          utf16TextFile,
+          emptyFile,
+          dataUrlFile0,
+          dataUrlFile1,
+          dataUrlFile2,
+        },
+        data: {
+          text: testTextData,
+          ascii: testASCIIData,
+          binary: testBinaryData,
+          url0: dataurldata0,
+          url1: dataurldata1,
+          url2: dataurldata2,
+        },
+      });
+    });
+
+    opener.sendAsyncMessage("files.open", [
+      testASCIIData,
+      testBinaryData,
+      null,
+      convertToUTF8(testTextData),
+      convertToUTF16(testTextData),
+      "",
+      dataurldata0,
+      dataurldata1,
+      dataurldata2,
+    ]);
+  });
+}
+
+function runBasicTests(data) {
+  return test_basic()
+    .then(() => {
+      return test_readAsText(data.blobs.asciiFile, data.data.ascii);
+    })
+    .then(() => {
+      return test_readAsBinaryString(data.blobs.binaryFile, data.data.binary);
+    })
+    .then(() => {
+      return test_readAsArrayBuffer(data.blobs.binaryFile, data.data.binary);
+    });
+}
+
+function runEncodingTests(data) {
+  return test_readAsTextWithEncoding(
+    data.blobs.asciiFile,
+    data.data.ascii,
+    data.data.ascii.length,
+    ""
+  )
+    .then(() => {
+      return test_readAsTextWithEncoding(
+        data.blobs.asciiFile,
+        data.data.ascii,
+        data.data.ascii.length,
+        "iso8859-1"
+      );
+    })
+    .then(() => {
+      return test_readAsTextWithEncoding(
+        data.blobs.utf8TextFile,
+        data.data.text,
+        convertToUTF8(data.data.text).length,
+        "utf8"
+      );
+    })
+    .then(() => {
+      return test_readAsTextWithEncoding(
+        data.blobs.utf16TextFile,
+        data.data.text,
+        convertToUTF16(data.data.text).length,
+        "utf-16"
+      );
+    })
+    .then(() => {
+      return test_readAsTextWithEncoding(data.blobs.emptyFile, "", 0, "");
+    })
+    .then(() => {
+      return test_readAsTextWithEncoding(data.blobs.emptyFile, "", 0, "utf8");
+    })
+    .then(() => {
+      return test_readAsTextWithEncoding(data.blobs.emptyFile, "", 0, "utf-16");
+    });
+}
+
+function runEmptyTests(data) {
+  return test_onlyResult()
+    .then(() => {
+      return test_readAsText(data.blobs.emptyFile, "");
+    })
+    .then(() => {
+      return test_readAsBinaryString(data.blobs.emptyFile, "");
+    })
+    .then(() => {
+      return test_readAsArrayBuffer(data.blobs.emptyFile, "");
+    })
+    .then(() => {
+      return test_readAsDataURL(data.blobs.emptyFile, convertToDataURL(""), 0);
+    });
+}
+
+function runTwiceTests(data) {
+  return test_readAsTextTwice(data.blobs.asciiFile, data.data.ascii)
+    .then(() => {
+      return test_readAsBinaryStringTwice(
+        data.blobs.binaryFile,
+        data.data.binary
+      );
+    })
+    .then(() => {
+      return test_readAsDataURLTwice(
+        data.blobs.binaryFile,
+        convertToDataURL(data.data.binary),
+        data.data.binary.length
+      );
+    })
+    .then(() => {
+      return test_readAsArrayBufferTwice(
+        data.blobs.binaryFile,
+        data.data.binary
+      );
+    })
+    .then(() => {
+      return test_readAsArrayBufferTwice2(
+        data.blobs.binaryFile,
+        data.data.binary
+      );
+    });
+}
+
+function runOtherTests(data) {
+  return test_readAsDataURL_customLength(
+    data.blobs.dataUrlFile0,
+    convertToDataURL(data.data.url0),
+    data.data.url0.length,
+    0
+  )
+    .then(() => {
+      return test_readAsDataURL_customLength(
+        data.blobs.dataUrlFile1,
+        convertToDataURL(data.data.url1),
+        data.data.url1.length,
+        1
+      );
+    })
+    .then(() => {
+      return test_readAsDataURL_customLength(
+        data.blobs.dataUrlFile2,
+        convertToDataURL(data.data.url2),
+        data.data.url2.length,
+        2
+      );
+    })
+    .then(() => {
+      return test_abort(data.blobs.asciiFile);
+    })
+    .then(() => {
+      return test_abort_readAsX(data.blobs.asciiFile, data.data.ascii);
+    })
+    .then(() => {
+      return test_nonExisting(data.blobs.nonExistingFile);
+    });
+}
+
+function convertToUTF16(s) {
+  let res = "";
+  for (let i = 0; i < s.length; ++i) {
+    c = s.charCodeAt(i);
+    res += String.fromCharCode(c & 255, c >>> 8);
+  }
+  return res;
+}
+
+function convertToUTF8(s) {
+  return unescape(encodeURIComponent(s));
+}
+
+function convertToDataURL(s) {
+  return "data:application/octet-stream;base64," + btoa(s);
+}
+
+function loadEventHandler_string(
+  event,
+  resolve,
+  reader,
+  data,
+  dataLength,
+  testName
+) {
+  is(event.target, reader, "Correct target.");
+  is(
+    event.target.readyState,
+    FileReader.DONE,
+    "readyState in test " + testName
+  );
+  is(event.target.error, null, "no error in test " + testName);
+  is(event.target.result, data, "result in test " + testName);
+  is(event.lengthComputable, true, "lengthComputable in test " + testName);
+  is(event.loaded, dataLength, "loaded in test " + testName);
+  is(event.total, dataLength, "total in test " + testName);
+  resolve();
+}
+
+function loadEventHandler_arrayBuffer(event, resolve, reader, data, testName) {
+  is(
+    event.target.readyState,
+    FileReader.DONE,
+    "readyState in test " + testName
+  );
+  is(event.target.error, null, "no error in test " + testName);
+  is(event.lengthComputable, true, "lengthComputable in test " + testName);
+  is(event.loaded, data.length, "loaded in test " + testName);
+  is(event.total, data.length, "total in test " + testName);
+  is(
+    event.target.result.byteLength,
+    data.length,
+    "array buffer size in test " + testName
+  );
+
+  let u8v = new Uint8Array(event.target.result);
+  is(
+    String.fromCharCode.apply(String, u8v),
+    data,
+    "array buffer contents in test " + testName
+  );
+  u8v = null;
+
+  if ("SpecialPowers" in self) {
+    SpecialPowers.gc();
+
+    is(
+      event.target.result.byteLength,
+      data.length,
+      "array buffer size after gc in test " + testName
+    );
+    u8v = new Uint8Array(event.target.result);
+    is(
+      String.fromCharCode.apply(String, u8v),
+      data,
+      "array buffer contents after gc in test " + testName
+    );
+  }
+
+  resolve();
+}
+
+function test_basic() {
+  return new Promise(resolve => {
+    is(FileReader.EMPTY, 0, "correct EMPTY value");
+    is(FileReader.LOADING, 1, "correct LOADING value");
+    is(FileReader.DONE, 2, "correct DONE value");
+    resolve();
+  });
+}
+
+function test_readAsText(blob, text) {
+  return new Promise(resolve => {
+    let onloadHasRun = false;
+    let onloadStartHasRun = false;
+
+    let r = new FileReader();
+    is(r.readyState, FileReader.EMPTY, "correct initial text readyState");
+
+    r.onload = event => {
+      loadEventHandler_string(
+        event,
+        resolve,
+        r,
+        text,
+        text.length,
+        "readAsText"
+      );
+    };
+
+    r.addEventListener("load", () => {
+      onloadHasRun = true;
+    });
+    r.addEventListener("loadstart", () => {
+      onloadStartHasRun = true;
+    });
+
+    r.readAsText(blob);
+
+    is(r.readyState, FileReader.LOADING, "correct loading text readyState");
+    is(onloadHasRun, false, "text loading must be async");
+    is(onloadStartHasRun, false, "text loadstart should fire async");
+  });
+}
+
+function test_readAsBinaryString(blob, text) {
+  return new Promise(resolve => {
+    let onloadHasRun = false;
+    let onloadStartHasRun = false;
+
+    let r = new FileReader();
+    is(r.readyState, FileReader.EMPTY, "correct initial binary readyState");
+
+    r.addEventListener("load", function() {
+      onloadHasRun = true;
+    });
+    r.addEventListener("loadstart", function() {
+      onloadStartHasRun = true;
+    });
+
+    r.readAsBinaryString(blob);
+
+    r.onload = event => {
+      loadEventHandler_string(
+        event,
+        resolve,
+        r,
+        text,
+        text.length,
+        "readAsBinaryString"
+      );
+    };
+
+    is(r.readyState, FileReader.LOADING, "correct loading binary readyState");
+    is(onloadHasRun, false, "binary loading must be async");
+    is(onloadStartHasRun, false, "binary loadstart should fire async");
+  });
+}
+
+function test_readAsArrayBuffer(blob, text) {
+  return new Promise(resolve => {
+    let onloadHasRun = false;
+    let onloadStartHasRun = false;
+
+    r = new FileReader();
+    is(
+      r.readyState,
+      FileReader.EMPTY,
+      "correct initial arrayBuffer readyState"
+    );
+
+    r.addEventListener("load", function() {
+      onloadHasRun = true;
+    });
+    r.addEventListener("loadstart", function() {
+      onloadStartHasRun = true;
+    });
+
+    r.readAsArrayBuffer(blob);
+
+    r.onload = event => {
+      loadEventHandler_arrayBuffer(
+        event,
+        resolve,
+        r,
+        text,
+        "readAsArrayBuffer"
+      );
+    };
+
+    is(
+      r.readyState,
+      FileReader.LOADING,
+      "correct loading arrayBuffer readyState"
+    );
+    is(onloadHasRun, false, "arrayBuffer loading must be async");
+    is(onloadStartHasRun, false, "arrayBuffer loadstart should fire sync");
+  });
+}
+
+// Test a variety of encodings, and make sure they work properly
+function test_readAsTextWithEncoding(blob, text, length, charset) {
+  return new Promise(resolve => {
+    let r = new FileReader();
+    r.onload = event => {
+      loadEventHandler_string(
+        event,
+        resolve,
+        r,
+        text,
+        length,
+        "readAsText-" + charset
+      );
+    };
+    r.readAsText(blob, charset);
+  });
+}
+
+// Test get result without reading
+function test_onlyResult() {
+  return new Promise(resolve => {
+    let r = new FileReader();
+    is(
+      r.readyState,
+      FileReader.EMPTY,
+      "readyState in test reader get result without reading"
+    );
+    is(r.error, null, "no error in test reader get result without reading");
+    is(r.result, null, "result in test reader get result without reading");
+    resolve();
+  });
+}
+
+function test_readAsDataURL(blob, text, length) {
+  return new Promise(resolve => {
+    let r = new FileReader();
+    r.onload = event => {
+      loadEventHandler_string(event, resolve, r, text, length, "readAsDataURL");
+    };
+    r.readAsDataURL(blob);
+  });
+}
+
+// Test reusing a FileReader to read multiple times
+function test_readAsTextTwice(blob, text) {
+  return new Promise(resolve => {
+    let r = new FileReader();
+    r.onload = event => {
+      loadEventHandler_string(
+        event,
+        () => {},
+        r,
+        text,
+        text.length,
+        "readAsText-reused-once"
+      );
+    };
+
+    let anotherListener = event => {
+      let r1 = event.target;
+      r1.removeEventListener("load", anotherListener);
+      r1.onload = evt => {
+        loadEventHandler_string(
+          evt,
+          resolve,
+          r1,
+          text,
+          text.length,
+          "readAsText-reused-twice"
+        );
+      };
+      r1.readAsText(blob);
+    };
+
+    r.addEventListener("load", anotherListener);
+    r.readAsText(blob);
+  });
+}
+
+// Test reusing a FileReader to read multiple times
+function test_readAsBinaryStringTwice(blob, text) {
+  return new Promise(resolve => {
+    let r = new FileReader();
+    r.onload = event => {
+      loadEventHandler_string(
+        event,
+        () => {},
+        r,
+        text,
+        text.length,
+        "readAsBinaryString-reused-once"
+      );
+    };
+
+    let anotherListener = event => {
+      let r1 = event.target;
+      r1.removeEventListener("load", anotherListener);
+      r1.onload = evt => {
+        loadEventHandler_string(
+          evt,
+          resolve,
+          r1,
+          text,
+          text.length,
+          "readAsBinaryString-reused-twice"
+        );
+      };
+      r1.readAsBinaryString(blob);
+    };
+
+    r.addEventListener("load", anotherListener);
+    r.readAsBinaryString(blob);
+  });
+}
+
+function test_readAsDataURLTwice(blob, text, length) {
+  return new Promise(resolve => {
+    let r = new FileReader();
+    r.onload = event => {
+      loadEventHandler_string(
+        event,
+        () => {},
+        r,
+        text,
+        length,
+        "readAsDataURL-reused-once"
+      );
+    };
+
+    let anotherListener = event => {
+      let r1 = event.target;
+      r1.removeEventListener("load", anotherListener);
+      r1.onload = evt => {
+        loadEventHandler_string(
+          evt,
+          resolve,
+          r1,
+          text,
+          length,
+          "readAsDataURL-reused-twice"
+        );
+      };
+      r1.readAsDataURL(blob);
+    };
+
+    r.addEventListener("load", anotherListener);
+    r.readAsDataURL(blob);
+  });
+}
+
+function test_readAsArrayBufferTwice(blob, text) {
+  return new Promise(resolve => {
+    let r = new FileReader();
+    r.onload = event => {
+      loadEventHandler_arrayBuffer(
+        event,
+        () => {},
+        r,
+        text,
+        "readAsArrayBuffer-reused-once"
+      );
+    };
+
+    let anotherListener = event => {
+      let r1 = event.target;
+      r1.removeEventListener("load", anotherListener);
+      r1.onload = evt => {
+        loadEventHandler_arrayBuffer(
+          evt,
+          resolve,
+          r1,
+          text,
+          "readAsArrayBuffer-reused-twice"
+        );
+      };
+      r1.readAsArrayBuffer(blob);
+    };
+
+    r.addEventListener("load", anotherListener);
+    r.readAsArrayBuffer(blob);
+  });
+}
+
+// Test first reading as ArrayBuffer then read as something else (BinaryString)
+// and doesn't crash
+function test_readAsArrayBufferTwice2(blob, text) {
+  return new Promise(resolve => {
+    let r = new FileReader();
+    r.onload = event => {
+      loadEventHandler_arrayBuffer(
+        event,
+        () => {},
+        r,
+        text,
+        "readAsArrayBuffer-reused-once2"
+      );
+    };
+
+    let anotherListener = event => {
+      let r1 = event.target;
+      r1.removeEventListener("load", anotherListener);
+      r1.onload = evt => {
+        loadEventHandler_string(
+          evt,
+          resolve,
+          r1,
+          text,
+          text.length,
+          "readAsArrayBuffer-reused-twice2"
+        );
+      };
+      r1.readAsBinaryString(blob);
+    };
+
+    r.addEventListener("load", anotherListener);
+    r.readAsArrayBuffer(blob);
+  });
+}
+
+function test_readAsDataURL_customLength(blob, text, length, numb) {
+  return new Promise(resolve => {
+    is(length % 3, numb, "Want to test data with length %3 == " + numb);
+    let r = new FileReader();
+    r.onload = event => {
+      loadEventHandler_string(
+        event,
+        resolve,
+        r,
+        text,
+        length,
+        "dataurl reading, %3 = " + numb
+      );
+    };
+    r.readAsDataURL(blob);
+  });
+}
+
+// Test abort()
+function test_abort(blob) {
+  return new Promise(resolve => {
+    let abortHasRun = false;
+    let loadEndHasRun = false;
+
+    let r = new FileReader();
+
+    r.onabort = function(event) {
+      is(abortHasRun, false, "abort should only fire once");
+      is(loadEndHasRun, false, "loadend shouldn't have fired yet");
+      abortHasRun = true;
+      is(
+        event.target.readyState,
+        FileReader.DONE,
+        "should be DONE while firing onabort"
+      );
+      is(
+        event.target.error.name,
+        "AbortError",
+        "error set to AbortError for aborted reads"
+      );
+      is(
+        event.target.result,
+        null,
+        "file data should be null on aborted reads"
+      );
+    };
+
+    r.onloadend = function(event) {
+      is(abortHasRun, true, "abort should fire before loadend");
+      is(loadEndHasRun, false, "loadend should only fire once");
+      loadEndHasRun = true;
+      is(
+        event.target.readyState,
+        FileReader.DONE,
+        "should be DONE while firing onabort"
+      );
+      is(
+        event.target.error.name,
+        "AbortError",
+        "error set to AbortError for aborted reads"
+      );
+      is(
+        event.target.result,
+        null,
+        "file data should be null on aborted reads"
+      );
+    };
+
+    r.onload = function() {
+      ok(false, "load should not fire for aborted reads");
+    };
+    r.onerror = function() {
+      ok(false, "error should not fire for aborted reads");
+    };
+    r.onprogress = function() {
+      ok(false, "progress should not fire for aborted reads");
+    };
+
+    let abortThrew = false;
+    try {
+      r.abort();
+    } catch (e) {
+      abortThrew = true;
+    }
+
+    is(abortThrew, false, "abort() doesn't throw");
+    is(abortHasRun, false, "abort() is a no-op unless loading");
+
+    r.readAsText(blob);
+    r.abort();
+
+    is(abortHasRun, true, "abort should fire sync");
+    is(loadEndHasRun, true, "loadend should fire sync");
+
+    resolve();
+  });
+}
+
+// Test calling readAsX to cause abort()
+function test_abort_readAsX(blob, text) {
+  return new Promise(resolve => {
+    let reuseAbortHasRun = false;
+
+    let r = new FileReader();
+    r.onabort = function(event) {
+      is(reuseAbortHasRun, false, "abort should only fire once");
+      reuseAbortHasRun = true;
+      is(
+        event.target.readyState,
+        FileReader.DONE,
+        "should be DONE while firing onabort"
+      );
+      is(
+        event.target.error.name,
+        "AbortError",
+        "error set to AbortError for aborted reads"
+      );
+      is(
+        event.target.result,
+        null,
+        "file data should be null on aborted reads"
+      );
+    };
+    r.onload = function() {
+      ok(false, "load should fire for nested reads");
+    };
+
+    let abortThrew = false;
+    try {
+      r.abort();
+    } catch (e) {
+      abortThrew = true;
+    }
+
+    is(abortThrew, false, "abort() should not throw");
+    is(reuseAbortHasRun, false, "abort() is a no-op unless loading");
+    r.readAsText(blob);
+
+    let readThrew = false;
+    try {
+      r.readAsText(blob);
+    } catch (e) {
+      readThrew = true;
+    }
+
+    is(readThrew, true, "readAsText() must throw if loading");
+    is(reuseAbortHasRun, false, "abort should not fire");
+
+    r.onload = event => {
+      loadEventHandler_string(
+        event,
+        resolve,
+        r,
+        text,
+        text.length,
+        "reuse-as-abort reading"
+      );
+    };
+  });
+}
+
+// Test reading from nonexistent files
+function test_nonExisting(blob) {
+  return new Promise(resolve => {
+    let r = new FileReader();
+
+    r.onerror = function(event) {
+      is(
+        event.target.readyState,
+        FileReader.DONE,
+        "should be DONE while firing onerror"
+      );
+      is(
+        event.target.error.name,
+        "NotFoundError",
+        "error set to NotFoundError for nonexistent files"
+      );
+      is(
+        event.target.result,
+        null,
+        "file data should be null on aborted reads"
+      );
+      resolve();
+    };
+    r.onload = function(event) {
+      is(false, "nonexistent file shouldn't load! (FIXME: bug 1122788)");
+    };
+
+    let didThrow = false;
+    try {
+      r.readAsDataURL(blob);
+    } catch (ex) {
+      didThrow = true;
+    }
+
+    // Once this test passes, we should test that onerror gets called and
+    // that the FileReader object is in the right state during that call.
+    is(
+      didThrow,
+      false,
+      "shouldn't throw when opening nonexistent file, should fire error instead"
+    );
+  });
+}
diff --git a/dom/file/tests/crashtests/1480354.html b/dom/file/tests/crashtests/1480354.html
new file mode 100644
index 0000000000..19e53bb1ca
--- /dev/null
+++ b/dom/file/tests/crashtests/1480354.html
@@ -0,0 +1,14 @@
+<html>
+<body>
+  <script>
+function createBlob(blocksize) {
+  var blob = new Blob();
+  while (blob.size < 25 * 1024 * 1024) { // 25 MB
+    blob = new Blob([blob, new Uint8Array(blocksize)]);
+  }
+  URL.createObjectURL(blob);
+}
+createBlob(1024 * 25);
+  </script>
+</body>
+</html>
diff --git a/dom/file/tests/crashtests/1562891.html b/dom/file/tests/crashtests/1562891.html
new file mode 100644
index 0000000000..fff7606a8a
--- /dev/null
+++ b/dom/file/tests/crashtests/1562891.html
@@ -0,0 +1,16 @@
+<html>
+<head>
+  <script>
+    function start () {
+      const canvas = document.createElementNS('http://www.w3.org/1999/xhtml', 'canvas')
+      SpecialPowers.forceGC();
+      canvas.toBlob(function (blob) {
+        blob.stream()
+        blob.arrayBuffer().then(() => {})
+      })
+    }
+
+    window.addEventListener('load', start)
+  </script>
+</head>
+</html>
diff --git a/dom/file/tests/crashtests/1747185.html b/dom/file/tests/crashtests/1747185.html
new file mode 100644
index 0000000000..89af55504f
--- /dev/null
+++ b/dom/file/tests/crashtests/1747185.html
@@ -0,0 +1,11 @@
+<html>
+<head>
+  <script>
+    window.addEventListener('load', () => {
+      let a = new Blob([new Uint8Array(2147483647)])
+      let b = new File([a], '')
+      b.stream()
+    })
+  </script>
+</head>
+</html>
diff --git a/dom/file/tests/crashtests/1748342.html b/dom/file/tests/crashtests/1748342.html
new file mode 100644
index 0000000000..5f0811b5bb
--- /dev/null
+++ b/dom/file/tests/crashtests/1748342.html
@@ -0,0 +1,26 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <script id="worker1" type="javascript/worker">
+    self.onmessage = async function (e) {
+      self.close()
+      const reader = new FileReader()
+      for (let i = 0; i < 25; i++) {
+        try { reader.readAsBinaryString(e.data[0]) } catch (e) {}
+      }
+      reader.addEventListener("progress", () => {}, {})
+    }
+  </script>
+  <script>
+    window.addEventListener("load", () => {
+      const script = new Blob([document.querySelector("#worker1").textContent], { type: "text/javascript" })
+      const worker = new Worker(window.URL.createObjectURL(script))
+      const data = new Blob(["70𯸟\nℽ㮼٠𛪇\0𛃧كe۰҅妽󠶖󠙻𝅧𡴶𝌋쮁偵9󠰾󠋼7\r𐇽0🥂.\b፟+⍳፟D󠢪3𣚽󠜎🐾�c_߰a<<=𝅦9𝆭𛰅9󠵼ௌ󠌌𖓄ΐ0�⡖‑뢈/-᭰*٠٪᷁e �𯯐𯬓𯕏‫‑걢V*=­￿**󠛐\u2028שּׁ&‭0󠄯𒡯e\n𛰵󠥿⁤𫍰,󠶒𝅥t\nl𧶈a𦜠09k𯔆䴋�|󠄷🦻𛝫󠁥𖭄", "*𒗬۰0\u2029‌/\n\r+󠎔𖼣k*=🿹𯀊\r٪\r󠳐𝲍慑B�\r󠮱\r\n\"\r\\𯉆۹c卑4󠣰󠻬鴗ꛌ\0⌕:\r\n𝚨9ꛅ٠󠃭𯋾\nJ󠯲9\rﾞ鈷P\u2029҉󠷒۹e \b緁︡𤆥^𯏂゚੿|٫󠕉揅ᷛ𩊜s𯑳2凅9c8H𦰤-\f%٠𨮫󠚵‑2𫈮P𝋄窥57\n-゙҄H󠭗𯪞𣃂-ᷢשּׁ貌솽|𝉃‬c㙡𯐉᭯mL\r"], {
+        "type": "image/png",
+        "endings": "transparent"
+      })
+      worker.postMessage([data], [])
+    })
+  </script>
+</head>
+</html>
diff --git a/dom/file/tests/crashtests/crashtests.list b/dom/file/tests/crashtests/crashtests.list
new file mode 100644
index 0000000000..22eec1962e
--- /dev/null
+++ b/dom/file/tests/crashtests/crashtests.list
@@ -0,0 +1,4 @@
+skip-if(ThreadSanitizer) load 1480354.html
+load 1562891.html
+skip-if(Android||ThreadSanitizer) load 1747185.html # Crashes on Android, times out on TSan.
+load 1748342.html
diff --git a/dom/file/tests/create_file_objects.js b/dom/file/tests/create_file_objects.js
new file mode 100644
index 0000000000..6243f4b8ab
--- /dev/null
+++ b/dom/file/tests/create_file_objects.js
@@ -0,0 +1,19 @@
+/* eslint-env mozilla/chrome-script */
+
+Cu.importGlobalProperties(["File"]);
+
+addMessageListener("create-file-objects", function(message) {
+  let files = [];
+  let promises = [];
+  for (fileName of message.fileNames) {
+    promises.push(
+      File.createFromFileName(fileName).then(function(file) {
+        files.push(file);
+      })
+    );
+  }
+
+  Promise.all(promises).then(function() {
+    sendAsyncMessage("created-file-objects", files);
+  });
+});
diff --git a/dom/file/tests/file_blobURL_expiring.html b/dom/file/tests/file_blobURL_expiring.html
new file mode 100644
index 0000000000..a1ae725709
--- /dev/null
+++ b/dom/file/tests/file_blobURL_expiring.html
@@ -0,0 +1,4 @@
+<script>
+var blob = new Blob([123]);
+parent.postMessage(URL.createObjectURL(blob), "*");
+</script>
diff --git a/dom/file/tests/file_mozfiledataurl_audio.ogg b/dom/file/tests/file_mozfiledataurl_audio.ogg
new file mode 100644
index 0000000000..88b2c1b5b2
--- /dev/null
+++ b/dom/file/tests/file_mozfiledataurl_audio.ogg
diff --git a/dom/file/tests/file_mozfiledataurl_doc.html b/dom/file/tests/file_mozfiledataurl_doc.html
new file mode 100644
index 0000000000..763b20a0f9
--- /dev/null
+++ b/dom/file/tests/file_mozfiledataurl_doc.html
@@ -0,0 +1,6 @@
+<!doctype html>
+<html>
+<body>
+<p>This here is a document!</p>
+<img id=img src="file_mozfiledataurl_img.jpg">
+</html>
diff --git a/dom/file/tests/file_mozfiledataurl_img.jpg b/dom/file/tests/file_mozfiledataurl_img.jpg
new file mode 100644
index 0000000000..dcd99b9670
--- /dev/null
+++ b/dom/file/tests/file_mozfiledataurl_img.jpg
diff --git a/dom/file/tests/file_mozfiledataurl_inner.html b/dom/file/tests/file_mozfiledataurl_inner.html
new file mode 100644
index 0000000000..a2e539bef7
--- /dev/null
+++ b/dom/file/tests/file_mozfiledataurl_inner.html
@@ -0,0 +1,76 @@
+<!doctype html>
+<html>
+<script type="application/javascript">
+var img;
+var audio;
+var iframe;
+
+addEventListener("message", function(e) {
+  mess = JSON.parse(e.data);
+  
+  if ("img" in mess)
+    img.src = mess.img;
+  else if ("audio" in mess)
+    audio.src = mess.audio
+  else if ("iframe" in mess)
+    iframe.src = mess.iframe;
+  else if ("xhr" in mess) {
+    let xhr = new XMLHttpRequest();
+    xhr.onerror = function() {
+      sendItUp({ didError: true });
+    }
+    xhr.onload = function() {
+      sendItUp({ text: xhr.responseText });
+    }
+    try {
+      xhr.open("GET", mess.xhr);
+      xhr.send();
+    }
+    catch (ex) {
+      sendItUp({ didThrow: true });
+    }
+  }
+
+}, false);
+
+function sendItUp(obj) {
+  window.parent.postMessage(JSON.stringify(obj), "*");
+}
+
+function audioNotifyParent(e) {
+  sendItUp({ type: e.type });
+}
+
+function imgNotifyParent(e) {
+  sendItUp({ type: e.type,
+             width: e.target.width,
+             height: e.target.height });
+}
+
+function iframeNotifyParent(e) {
+  res = { type: e.type };
+  try {
+    res.text = e.target.contentDocument.getElementsByTagName("p")[0].textContent;
+  } catch (ex) {}
+  try {
+    res.imgWidth = e.target.contentDocument.getElementById("img").width;
+  } catch (ex) {}
+
+  sendItUp(res);
+}
+
+onload = function() {
+  img = document.getElementById('img');
+  img.onerror = img.onload = imgNotifyParent;
+  iframe = document.getElementById('iframe');
+  iframe.onerror = iframe.onload = iframeNotifyParent;
+  audio = document.getElementById('audio');
+  audio.onerror = audio.onloadeddata = audioNotifyParent;
+}
+
+</script>
+<body>
+<img id=img>
+<audio id=audio>
+<iframe id=iframe></iframe>
+</html>
diff --git a/dom/file/tests/file_mozfiledataurl_text.txt b/dom/file/tests/file_mozfiledataurl_text.txt
new file mode 100644
index 0000000000..315338aa9b
--- /dev/null
+++ b/dom/file/tests/file_mozfiledataurl_text.txt
@@ -0,0 +1 @@
+Yarr, here be plaintext file, ya landlubber
diff --git a/dom/file/tests/file_nonascii_blob_url.html b/dom/file/tests/file_nonascii_blob_url.html
new file mode 100644
index 0000000000..89183f4613
--- /dev/null
+++ b/dom/file/tests/file_nonascii_blob_url.html
@@ -0,0 +1,24 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Test blob URL for non-ascii domain</title>
+</head>
+<body>
+  <p id="result"></p>
+  <script type="application/javascript">
+
+window.onmessage = function(e) {
+  var blob = new Blob([e.data]);
+  var url = URL.createObjectURL(blob);
+
+  var xhr = new XMLHttpRequest();
+  xhr.open('GET', url, false);
+  xhr.send(null);
+
+  parent.postMessage(xhr.responseText, '*');
+}
+
+  </script>
+</body>
+</html>
diff --git a/dom/file/tests/fileapi_chromeScript.js b/dom/file/tests/fileapi_chromeScript.js
new file mode 100644
index 0000000000..dd949bae64
--- /dev/null
+++ b/dom/file/tests/fileapi_chromeScript.js
@@ -0,0 +1,54 @@
+/* eslint-env mozilla/chrome-script */
+
+Cu.importGlobalProperties(["File"]);
+
+function createFileWithData(fileData) {
+  var willDelete = fileData === null;
+
+  var dirSvc = Cc["@mozilla.org/file/directory_service;1"].getService(
+    Ci.nsIProperties
+  );
+
+  var testFile = dirSvc.get("ProfD", Ci.nsIFile);
+  testFile.append("fileAPItestfile");
+  testFile.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, 0o600);
+
+  var outStream = Cc[
+    "@mozilla.org/network/file-output-stream;1"
+  ].createInstance(Ci.nsIFileOutputStream);
+  outStream.init(
+    testFile,
+    0x02 | 0x08 | 0x20, // write, create, truncate
+    0o666,
+    0
+  );
+  if (willDelete) {
+    fileData = "some irrelevant test data\n";
+  }
+  outStream.write(fileData, fileData.length);
+  outStream.close();
+  return File.createFromNsIFile(testFile).then(domFile => {
+    if (willDelete) {
+      testFile.remove(/* recursive: */ false);
+    }
+
+    return domFile;
+  });
+}
+
+addMessageListener("files.open", function(message) {
+  let promises = [];
+  let list = [];
+
+  for (let fileData of message) {
+    promises.push(
+      createFileWithData(fileData).then(domFile => {
+        list.push(domFile);
+      })
+    );
+  }
+
+  Promise.all(promises).then(() => {
+    sendAsyncMessage("files.opened", list);
+  });
+});
diff --git a/dom/file/tests/mochitest.ini b/dom/file/tests/mochitest.ini
new file mode 100644
index 0000000000..e1c62791e3
--- /dev/null
+++ b/dom/file/tests/mochitest.ini
@@ -0,0 +1,48 @@
+[DEFAULT]
+support-files =
+  common_blob.js
+  create_file_objects.js
+  common_fileReader.js
+  common_blob_types.js
+  file_blobURL_expiring.html
+  file_mozfiledataurl_img.jpg
+  file_mozfiledataurl_audio.ogg
+  file_mozfiledataurl_doc.html
+  file_mozfiledataurl_text.txt
+  file_mozfiledataurl_inner.html
+  file_nonascii_blob_url.html
+  fileapi_chromeScript.js
+  worker_fileReader.js
+  !/dom/html/test/form_submit_server.sjs
+  !/dom/xhr/tests/file_XHRSendData.sjs
+  !/dom/xhr/tests/temporaryFileBlob.sjs
+
+[test_blob_fragment_and_query.html]
+[test_blobconstructor.html]
+[test_blobURL_expiring.html]
+[test_file_from_blob.html]
+[test_nonascii_blob_url.html]
+[test_file_negative_date.html]
+[test_fileapi_basic.html]
+[test_fileapi_encoding.html]
+[test_fileapi_twice.html]
+[test_fileapi_other.html]
+[test_fileapi_basic_worker.html]
+[test_fileapi_encoding_worker.html]
+[test_fileapi_twice_worker.html]
+[test_fileapi_other_worker.html]
+[test_fileapi_slice_realFile_1.html]
+[test_fileapi_slice_realFile_2.html]
+skip-if = (verify && !debug && (os == 'win'))
+[test_fileapi_slice_memFile_1.html]
+[test_fileapi_slice_memFile_2.html]
+[test_fileapi_slice_image.html]
+[test_mozfiledataurl.html]
+skip-if = toolkit == 'android' #TIMED_OUT
+[test_bug1507893.html]
+support-files = worker_bug1507893.js
+[test_bug1742540.html]
+support-files = worker_bug1742540.js
+skip-if = toolkit == 'android' #TIMED_OUT
+[test_blob_reading.html]
+support-files = common_blob_reading.js worker_blob_reading.js
diff --git a/dom/file/tests/test_agentcluster_bloburl.js b/dom/file/tests/test_agentcluster_bloburl.js
new file mode 100644
index 0000000000..eb6377674f
--- /dev/null
+++ b/dom/file/tests/test_agentcluster_bloburl.js
@@ -0,0 +1,170 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+const { CookieXPCShellUtils } = ChromeUtils.import(
+  "resource://testing-common/CookieXPCShellUtils.jsm"
+);
+
+CookieXPCShellUtils.init(this);
+
+// Same agent cluster, all works fine: blobURLs can be opened.
+add_task(async () => {
+  do_get_profile();
+
+  // CookieXPCShellUtils.createServer does not support https
+  Services.prefs.setBoolPref("dom.security.https_first", false);
+
+  Services.prefs.setBoolPref(
+    "privacy.partition.bloburl_per_agent_cluster",
+    true
+  );
+
+  const server = CookieXPCShellUtils.createServer({ hosts: ["example.org"] });
+
+  let result = new Promise(resolve => {
+    server.registerPathHandler("/result", (metadata, response) => {
+      resolve(metadata.queryString == "ok");
+
+      const body = "Done";
+      response.bodyOutputStream.write(body, body.length);
+    });
+  });
+
+  server.registerPathHandler("/test", (metadata, response) => {
+    response.setStatusLine(metadata.httpVersion, 200, "OK");
+    response.setHeader("Content-Type", "text/html", false);
+    const body = `<script>
+      let b = new Blob(["Hello world!"]);
+      let u = URL.createObjectURL(b);
+      fetch(u).then(r => r.text()).then(t => {
+         if (t !== "Hello world!") {
+           throw new Error(42);
+         }
+      }).then(() => fetch("/result?ok"), () => fetch("/result?failure")).then(() => {});
+    </script>`;
+    response.bodyOutputStream.write(body, body.length);
+  });
+
+  let contentPage = await CookieXPCShellUtils.loadContentPage(
+    "http://example.org/test"
+  );
+
+  Assert.ok(await result, "BlobURL works");
+  await contentPage.close();
+});
+
+// Same agent cluster: frames
+add_task(async () => {
+  do_get_profile();
+
+  // CookieXPCShellUtils.createServer does not support https
+  Services.prefs.setBoolPref("dom.security.https_first", false);
+
+  const server = CookieXPCShellUtils.createServer({ hosts: ["example.org"] });
+
+  let result = new Promise(resolve => {
+    server.registerPathHandler("/result", (metadata, response) => {
+      resolve(metadata.queryString == "ok");
+
+      const body = "Done";
+      response.bodyOutputStream.write(body, body.length);
+    });
+  });
+
+  server.registerPathHandler("/iframe", (metadata, response) => {
+    response.setStatusLine(metadata.httpVersion, 200, "OK");
+    response.setHeader("Content-Type", "text/html", false);
+    const body = `<script>
+      fetch("${metadata.queryString}").then(r => r.text()).then(t => {
+         if (t !== "Hello world!") {
+           throw new Error(42);
+         }
+      }).then(() => fetch("/result?ok"), () => fetch("/result?failure")).then(() => {});
+    </script>`;
+    response.bodyOutputStream.write(body, body.length);
+  });
+
+  server.registerPathHandler("/test", (metadata, response) => {
+    response.setStatusLine(metadata.httpVersion, 200, "OK");
+    response.setHeader("Content-Type", "text/html", false);
+    const body = `<iframe id="a"></iframe><script>
+      let b = new Blob(["Hello world!"]);
+      let u = URL.createObjectURL(b);
+      document.getElementById("a").src = "/iframe?" + u;
+    </script>`;
+    response.bodyOutputStream.write(body, body.length);
+  });
+
+  let contentPage = await CookieXPCShellUtils.loadContentPage(
+    "http://example.org/test"
+  );
+
+  Assert.ok(await result, "BlobURL works");
+  await contentPage.close();
+});
+
+// Cross agent cluster: different tabs
+add_task(async () => {
+  do_get_profile();
+
+  const server = CookieXPCShellUtils.createServer({ hosts: ["example.org"] });
+
+  let result = new Promise(resolve => {
+    server.registerPathHandler("/result", (metadata, response) => {
+      resolve(metadata.queryString == "ok");
+
+      const body = "Done";
+      response.bodyOutputStream.write(body, body.length);
+    });
+  });
+
+  const step = new Promise(resolve => {
+    server.registerPathHandler("/step", (metadata, response) => {
+      resolve(metadata.queryString);
+      response.setStatusLine(metadata.httpVersion, 200, "OK");
+      response.setHeader("Content-Type", "text/html", false);
+      const body = "Thanks!";
+      response.bodyOutputStream.write(body, body.length);
+    });
+  });
+
+  server.registerPathHandler("/test", (metadata, response) => {
+    response.setStatusLine(metadata.httpVersion, 200, "OK");
+    response.setHeader("Content-Type", "text/html", false);
+    const body = `<script>
+      let b = new Blob(["Hello world!"]);
+      let u = URL.createObjectURL(b);
+      fetch("/step?" + u).then(() => {});
+    </script>`;
+    response.bodyOutputStream.write(body, body.length);
+  });
+
+  let contentPage = await CookieXPCShellUtils.loadContentPage(
+    "http://example.org/test"
+  );
+
+  const blobURL = await step;
+  Assert.ok(blobURL.length, "We have a blobURL");
+
+  server.registerPathHandler("/cross-test", (metadata, response) => {
+    response.setStatusLine(metadata.httpVersion, 200, "OK");
+    response.setHeader("Content-Type", "text/html", false);
+    const body = `<script>
+      fetch("${metadata.queryString}").then(r => r.text()).then(t => {
+         if (t !== "Hello world!") {
+           throw new Error(42);
+         }
+      }).then(() => fetch("/result?ok"), () => fetch("/result?failure")).then(() => {});
+    </script>`;
+    response.bodyOutputStream.write(body, body.length);
+  });
+
+  let contentPage2 = await CookieXPCShellUtils.loadContentPage(
+    "http://example.org/cross-test?" + blobURL
+  );
+
+  Assert.ok(!(await result), "BlobURL should not work");
+  await contentPage.close();
+  await contentPage2.close();
+});
diff --git a/dom/file/tests/test_blobURL_expiring.html b/dom/file/tests/test_blobURL_expiring.html
new file mode 100644
index 0000000000..7fdf461371
--- /dev/null
+++ b/dom/file/tests/test_blobURL_expiring.html
@@ -0,0 +1,48 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Test for Blob URI expiration</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+  <script>
+
+onmessage = function(e) {
+  var blobURL = e.data;
+
+  (new Promise(function(resolve, reject) {
+    var xhr = new XMLHttpRequest();
+    xhr.open("GET", blobURL);
+    xhr.send();
+    xhr.onload = function() {
+      is(xhr.response, "123", "Response matches!");
+      resolve();
+    }
+  })).then(function() {
+    document.body.removeChild(iframe);
+  }).then(function() {
+    var xhr = new XMLHttpRequest();
+    xhr.open("GET", blobURL);
+    xhr.onerror = function() {
+      ok(true, "The URL should be done!");
+      SimpleTest.finish();
+    }
+    xhr.onload = function() {
+      ok(false, "The URL should be done!");
+      SimpleTest.finish();
+    }
+    xhr.send();
+  });
+}
+
+var iframe = document.createElement('iframe');
+iframe.src = 'file_blobURL_expiring.html';
+document.body.appendChild(iframe);
+
+SimpleTest.waitForExplicitFinish();
+
+  </script>
+</body>
+</html>
diff --git a/dom/file/tests/test_blob_fragment_and_query.html b/dom/file/tests/test_blob_fragment_and_query.html
new file mode 100644
index 0000000000..fa3709c419
--- /dev/null
+++ b/dom/file/tests/test_blob_fragment_and_query.html
@@ -0,0 +1,62 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Test for Blob URI with fragments</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+  <script>
+
+var  blob = new Blob(['hello world']);
+ok(blob, "We have a blob.");
+
+var tests = [
+  { part: "", revoke: false, ok: true },
+  { part: "", revoke: true, ok: false },
+  { part: "?aa", revoke: false, ok: false },
+  { part: "?cc#dd", revoke: false, ok: false },
+  // Stripping #fragment on fetch
+  { part: "#bb", revoke: false, ok: true },
+  { part: "#ee?ff", revoke: false, ok: true }
+];
+
+function runTest() {
+  if (!tests.length) {
+    SimpleTest.finish();
+    return;
+  }
+
+  var url = URL.createObjectURL(blob);
+  ok(url, "We have a URI");
+
+  var test = tests.shift();
+
+  if (test.revoke) {
+    URL.revokeObjectURL(url + test.part);
+  }
+
+  var xhr = new XMLHttpRequest();
+  xhr.open('GET', url + test.part);
+
+  xhr.onload = function() {
+    ok(test.ok, `URL with "${test.part}" should send()`);
+    is(xhr.responseText, 'hello world', 'URL: ' + url + test.part);
+    runTest();
+  }
+
+  xhr.onerror = function() {
+    ok(!test.ok, `URL with "${test.part}" should fail on send()`);
+    runTest();
+  }
+
+  xhr.send();
+}
+
+SimpleTest.waitForExplicitFinish();
+runTest();
+
+  </script>
+</body>
+</html>
diff --git a/dom/file/tests/test_blob_reading.html b/dom/file/tests/test_blob_reading.html
new file mode 100644
index 0000000000..6efc5c4835
--- /dev/null
+++ b/dom/file/tests/test_blob_reading.html
@@ -0,0 +1,34 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Reading blobs</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="common_blob_reading.js"></script>
+  <script src="common_blob_types.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+  <script>
+
+SimpleTest.waitForExplicitFinish();
+
+async function runAllTests() {
+  let content = "hello world";
+  await forEachBlobType(content, async blob => {
+    await testBlobText(blob, content);
+    await workify('testBlobText', blob, content);
+
+    await testBlobArrayBuffer(blob, content);
+    await workify('testBlobArrayBuffer', blob, content);
+
+    await testBlobStream(blob, content);
+    await workify('testBlobStream', blob, content);
+  });
+}
+
+runAllTests().then(SimpleTest.finish);
+
+  </script>
+</body>
+</html>
diff --git a/dom/file/tests/test_blobconstructor.html b/dom/file/tests/test_blobconstructor.html
new file mode 100644
index 0000000000..d95444f9ea
--- /dev/null
+++ b/dom/file/tests/test_blobconstructor.html
@@ -0,0 +1,246 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=721569
+-->
+<head>
+  <title>Test for Blob constructor (Bug 721569)</title>
+  <script type="text/javascript" src="/MochiKit/MochiKit.js"></script>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="common_blob.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=721569">Mozilla Bug 721569</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+"use strict";
+/** Test for Bug 721569 **/
+var blob = new Blob();
+ok(blob, "Blob should exist");
+
+ok(blob.size !== undefined, "Blob should have a size property");
+ok(blob.type !== undefined, "Blob should have a type property");
+ok(blob.slice, "Blob should have a slice method");
+
+blob = new Blob([], {type: null});
+ok(blob, "Blob should exist");
+is(blob.type, "null", "Blob type should be stringified");
+
+blob = new Blob([], {type: undefined});
+ok(blob, "Blob should exist");
+is(blob.type, "", "Blob type should be treated as missing");
+
+try {
+blob = new Blob([]);
+ok(true, "an empty blobParts argument should not throw");
+} catch(e) {
+ok(false, "NOT REACHED");
+}
+
+try {
+blob = new Blob(null);
+ok(false, "NOT REACHED");
+} catch(e) {
+ok(true, "a null blobParts member should throw");
+}
+
+try {
+blob = new Blob([], null);
+ok(true, "a null options member should not throw");
+} catch(e) {
+ok(false, "NOT REACHED");
+}
+
+try {
+blob = new Blob([], undefined);
+ok(true, "an undefined options member should not throw");
+} catch(e) {
+ok(false, "NOT REACHED");
+}
+
+try {
+blob = new Blob([], false);
+ok(false, "NOT REACHED");
+} catch(e) {
+ok(true, "a boolean options member should throw");
+}
+
+try {
+blob = new Blob([], 0);
+ok(false, "NOT REACHED");
+} catch(e) {
+ok(true, "a numeric options member should throw");
+}
+
+try {
+blob = new Blob([], "");
+ok(false, "NOT REACHED");
+} catch(e) {
+ok(true, "a string options member should throw");
+}
+
+/** Test for dictionary initialization order **/
+(function() {
+  var o = {};
+  var p = {type: "text/plain", endings: "transparent"};
+  var called = [];
+  function add_to_called(n) {
+    called.push(n);
+    return p[n];
+  }
+  ["type", "endings"].forEach(function(n) {
+    Object.defineProperty(o, n, { get: add_to_called.bind(null, n) });
+  });
+  var b = new Blob([], o);
+  is(JSON.stringify(called), JSON.stringify(["endings", "type"]), "dictionary members should be get in lexicographical order");
+})();
+
+let blob1 = new Blob(["squiggle"]);
+ok(blob1 instanceof Blob, "Blob constructor should produce Blobs");
+ok(!(blob1 instanceof File), "Blob constructor should not produce Files");
+is(blob1.type, "", "Blob constructor with no options should return Blob with empty type");
+is(blob1.size, 8, "Blob constructor should return Blob with correct size");
+
+let blob2 = new Blob(["steak"], {type: "content/type"});
+ok(blob2 instanceof Blob, "Blob constructor should produce Blobs");
+ok(!(blob2 instanceof File), "Blob constructor should not produce Files");
+is(blob2.type, "content/type", "Blob constructor with a type option should return Blob with the type");
+is(blob2.size, 5, "Blob constructor should return Blob with correct size");
+
+
+let aB = new ArrayBuffer(16);
+var int8View = new Int8Array(aB);
+for (var i = 0; i < 16; i++) {
+  int8View[i] = i+65;
+}
+
+let testData =
+ [
+    // Test 3 strings
+    [["foo", "bar", "baz"], {},
+                            [{start: 0, length: 9, contents: "foobarbaz"},
+                             {start: 0, length: 3, contents: "foo"},
+                             {start: 3, length:6, contents:  "barbaz"},
+                             {start: 6, length: 3, contents:  "baz"},
+                             {start: 6, length: 6, contents: "baz"},
+                             {start: 0, length: 9, contents:  "foobarbaz"},
+                             {start: 0, length: 11, contents: "foobarbaz"},
+                             {start: 10, length: 5, contents: ""}]],
+    // Test string, Blob, string
+    [["foo", blob1, "baz"], {},
+                            [{start: 0, length: 3, contents:  "foo"},
+                             {start: 3, length: 8, contents:  "squiggle"},
+                             {start: 2, length: 2, contents:  "os"},
+                             {start: 10, length: 2, contents: "eb"}]],
+    // Test blob, string, blob
+    [[blob1, "foo", blob1], {},
+                            [{start: 0, length: 8, contents:  "squiggle"},
+                             {start: 7, length: 2, contents:  "ef"},
+                             {start: 10, length: 2, contents: "os"},
+                             {start: 1, length: 3, contents:  "qui"},
+                             {start: 12, length: 3, contents: "qui"},
+                             {start: 40, length: 20, contents: ""}]],
+    // Test blobs all the way down
+    [[blob2, blob1, blob2], {},
+                            [{start: 0, length: 5, contents:  "steak"},
+                             {start: 5, length: 8, contents:  "squiggle"},
+                             {start: 13, length: 5, contents: "steak"},
+                             {start: 1, length: 2, contents:  "te"},
+                             {start: 6, length: 4, contents:  "quig"}]],
+    // Test an array buffer
+    [[aB, blob1, "foo"], {},
+                            [{start: 0, length: 8, contents:  "ABCDEFGH"},
+                             {start: 8, length:10, contents:  "IJKLMNOPsq"},
+                             {start: 17, length: 3, contents: "qui"},
+                             {start: 4, length: 8, contents:  "EFGHIJKL"}]],
+    // Test an ArrayBufferView
+    [[int8View, blob1, "foo"], {},
+                            [{start: 0, length: 8, contents:  "ABCDEFGH"},
+                             {start: 8, length:10, contents:  "IJKLMNOPsq"},
+                             {start: 17, length: 3, contents: "qui"},
+                             {start: 4, length: 8, contents:  "EFGHIJKL"}]],
+    // Test a partial ArrayBufferView
+    [[new Uint8Array(aB, 3, 5), blob1, "foo"], {},
+                            [{start: 0, length: 8, contents:  "DEFGHsqu"},
+                             {start: 8, length:10, contents:  "igglefoo"},
+                             {start: 4, length: 8, contents:  "Hsquiggl"}]],
+    // Test transparent line endings
+    [["foo\r\n", "bar\r", "baz\n"], { endings: "transparent" },
+                            [{start: 0, length: 5, contents:  "foo\r\n"},
+                             {start: 5, length: 4, contents:  "bar\r"},
+                             {start: 9, length: 4, contents: "baz\n"}]],
+    // Test transparent line endings when the second argument is omitted
+    [["foo\r\n", "bar\r", "baz\n"], undefined,
+                            [{start: 0, length: 5, contents:  "foo\r\n"},
+                             {start: 5, length: 4, contents:  "bar\r"},
+                             {start: 9, length: 4, contents: "baz\n"}]],
+    // Test native line endings
+    [["foo\r\n", "bar\r", "baz\n"], { endings: "native" },
+                            navigator.platform.includes("Win") ?
+                            [{start: 0, length: 5, contents:  "foo\r\n"},
+                             {start: 5, length: 5, contents:  "bar\r\n"},
+                             {start: 10, length: 5, contents: "baz\r\n"}] :
+                            [{start: 0, length: 4, contents:  "foo\n"},
+                             {start: 4, length: 4, contents:  "bar\n"},
+                             {start: 8, length: 4, contents: "baz\n"}]],
+    // Test type coercion of a number
+    [[3, int8View, "foo"], {},
+                            [{start: 0, length: 8, contents:  "3ABCDEFG"},
+                             {start: 8, length:10, contents:  "HIJKLMNOPf"},
+                             {start: 17, length: 4, contents: "foo"},
+                             {start: 4, length: 8, contents:  "DEFGHIJK"}]]
+ ];
+
+let currentTest = null;
+let testCounter = 0;
+
+function runTests() {
+  if (!currentTest || !currentTest[2].length) {
+    if (!testData.length) {
+      SimpleTest.finish();
+      return;
+    }
+
+    currentTest = testData.shift();
+    ++testCounter;
+  }
+
+  let [blobs, options] = currentTest;
+  let test = currentTest[2].shift();
+
+  let blob3;
+  if (options !== undefined) {
+    blob3 = new Blob(blobs, options);
+  } else {
+    blob3 = new Blob(blobs);
+  }
+
+  ok(blob3, "Test " + testCounter + " got blob");
+  ok(blob3 instanceof Blob, "Test " + testCounter + " blob is a Blob");
+  ok(!(blob3 instanceof File), "Test " + testCounter + " blob is not a File");
+
+  let slice = blob3.slice(test.start, test.start + test.length);
+  ok(slice, "Test " + testCounter + " got slice");
+  ok(slice instanceof Blob, "Test " + testCounter + " slice is a Blob");
+  ok(!(slice instanceof File), "Test " + testCounter + " slice is not a File");
+  is(slice.size, test.contents.length, "Test " + testCounter + " slice is correct size");
+
+  testBlob(slice, test.contents, "Test " + testCounter).then(() => {
+    SpecialPowers.gc();
+    runTests();
+  });
+}
+
+SimpleTest.requestLongerTimeout(2);
+SimpleTest.waitForExplicitFinish();
+runTests();
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/file/tests/test_bloburi.js b/dom/file/tests/test_bloburi.js
new file mode 100644
index 0000000000..575b3a5ba1
--- /dev/null
+++ b/dom/file/tests/test_bloburi.js
@@ -0,0 +1,28 @@
+var ios = Cc["@mozilla.org/network/io-service;1"].getService(Ci.nsIIOService);
+
+var uris = [
+  {
+    uri: "blob:https://example.com/230d5d50-35f9-9745-a64a-15e47b731a81",
+    local: true,
+  },
+  {
+    uri: "rstp://1.2.3.4/some_path?param=a",
+    local: false,
+  },
+  {
+    uri: "moz-fonttable://something",
+    local: true,
+  },
+];
+
+function run_test() {
+  for (let i = 0; i < uris.length; i++) {
+    let uri = ios.newURI(uris[i].uri);
+    let flags = ios.getDynamicProtocolFlags(uri);
+
+    Assert.equal(
+      Ci.nsIProtocolHandler.URI_IS_LOCAL_RESOURCE & flags,
+      uris[i].local ? Ci.nsIProtocolHandler.URI_IS_LOCAL_RESOURCE : 0
+    );
+  }
+}
diff --git a/dom/file/tests/test_bug1507893.html b/dom/file/tests/test_bug1507893.html
new file mode 100644
index 0000000000..f0f83ff9ce
--- /dev/null
+++ b/dom/file/tests/test_bug1507893.html
@@ -0,0 +1,63 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Blob URLs fetched in workers</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+  <script>
+
+SimpleTest.waitForExplicitFinish();
+
+// Let's be positive.
+Promise.resolve()
+
+// Create a file.
+.then(_ => {
+  return new Promise(resolve => {
+    let openerURL = SimpleTest.getTestFileURL("fileapi_chromeScript.js");
+    let opener = SpecialPowers.loadChromeScript(openerURL);
+
+    opener.addMessageListener("files.opened", files => {
+      resolve(files[0]);
+    });
+
+    opener.sendAsyncMessage("files.open", [ "I am the blob content" ]);
+  })
+})
+
+// Just a couple of checks
+.then(file => {
+  ok(file instanceof File, "We want a file");
+  ok(file.size > 0, "We have content");
+  return file;
+})
+
+// Let's create a blobURL
+.then(file => URL.createObjectURL(file))
+
+// Let's send it to a worker.
+.then(url => {
+  return new Promise(resolve => {
+    let w = new Worker('worker_bug1507893.js');
+    w.onmessage = e => {
+     resolve(e.data);
+    };
+    w.postMessage(url);
+  });
+})
+
+// Let's check the worker's output
+.then(blob => {
+  ok(blob instanceof File, "The worker sends us a blob");
+  ok(blob.size > 0, "We have data");
+})
+
+// All done.
+.then(SimpleTest.finish);
+
+  </script>
+</body>
+</html>
diff --git a/dom/file/tests/test_bug1742540.html b/dom/file/tests/test_bug1742540.html
new file mode 100644
index 0000000000..7516f38a85
--- /dev/null
+++ b/dom/file/tests/test_bug1742540.html
@@ -0,0 +1,83 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Test for Bug 1742540</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+  <script>
+
+SimpleTest.waitForExplicitFinish();
+
+add_task(function setupPrefs() {
+  return SpecialPowers.pushPrefEnv({
+    set: [
+      ["dom.serviceWorkers.enabled", true],
+      ["dom.serviceWorkers.testing.enabled", true],
+    ],
+  });
+});
+
+function get_file() {
+  return new Promise(resolve => {
+    let xhr = new XMLHttpRequest();
+    xhr.open("GET", "/dynamic/getMyDirectory.sjs", false);
+    xhr.send();
+    let basePath = xhr.responseText;
+
+    let script = SpecialPowers.loadChromeScript(
+      SimpleTest.getTestFileURL("create_file_objects.js")
+    );
+    script.addMessageListener("created-file-objects", files => {
+      resolve(files[0]);
+    });
+    script.sendAsyncMessage("create-file-objects", {
+      fileNames: [basePath + "file_mozfiledataurl_audio.ogg"],
+    });
+  });
+}
+
+function wait_for_message(port, expected_message) {
+  return new Promise(resolve => {
+    port.onmessage = event => {
+      port.onmessage = null;
+      ok(event.data === expected_message, event.data);
+      resolve();
+    };
+  });
+}
+
+function unregister_and_done(registration) {
+  return registration.unregister().then(() => {
+    ok(true, "Will find leaks of nsPipe in BloatView without fix.");
+    SimpleTest.finish;
+  });
+}
+
+add_task(async function send_file_to_serviceworker() {
+  let registration = await navigator.serviceWorker
+    .register("worker_bug1742540.js", { scope: "./" })
+    .then(() => {
+      return navigator.serviceWorker.ready;
+    });
+
+  ok(registration.active, "ServiceWorker is activated");
+
+  let file = await get_file();
+  ok(file.size > 100000, "File size is big enough.");
+  let message = "ServiceWorker receives a file and did not reference it.";
+  let channel = new MessageChannel();
+  let received = wait_for_message(channel.port1, message);
+  registration.active.postMessage({ port: channel.port2, message, file }, [
+    channel.port2,
+  ]);
+  await received;
+
+  let finish = await unregister_and_done(registration);
+});
+
+  </script>
+</body>
+</html>
diff --git a/dom/file/tests/test_createFile.js b/dom/file/tests/test_createFile.js
new file mode 100644
index 0000000000..fd310a19f4
--- /dev/null
+++ b/dom/file/tests/test_createFile.js
@@ -0,0 +1,52 @@
+add_task(async function() {
+  do_get_profile();
+
+  let existingFile = Services.dirsvc
+    .QueryInterface(Ci.nsIProperties)
+    .get("ProfD", Ci.nsIFile);
+  existingFile.append("exists.js");
+  existingFile.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, 0o600);
+
+  var outStream = Cc[
+    "@mozilla.org/network/file-output-stream;1"
+  ].createInstance(Ci.nsIFileOutputStream);
+  outStream.init(
+    existingFile,
+    0x02 | 0x08 | 0x20, // write, create, truncate
+    0o666,
+    0
+  );
+
+  var fileData = "Hello World!";
+  outStream.write(fileData, fileData.length);
+  outStream.close();
+
+  ok(existingFile.exists(), "exists.js exists");
+
+  let unknownFile = Services.dirsvc
+    .QueryInterface(Ci.nsIProperties)
+    .get("TmpD", Ci.nsIFile);
+  unknownFile.append("wow.txt");
+
+  ok(!unknownFile.exists(), unknownFile.path + " doesn't exist");
+
+  let a = await File.createFromNsIFile(existingFile, { existenceCheck: false });
+  ok(a.size != 0, "The size is correctly set");
+
+  let b = await File.createFromNsIFile(unknownFile, { existenceCheck: false });
+  ok(b.size == 0, "The size is 0 for unknown file");
+
+  let c = await File.createFromNsIFile(existingFile, { existenceCheck: true });
+  ok(c.size != 0, "The size is correctly set");
+
+  let d = await File.createFromNsIFile(unknownFile, {
+    existenceCheck: true,
+  }).then(
+    _ => true,
+    _ => false
+  );
+  ok(d === false, "Exception thrown");
+
+  existingFile.remove(true);
+  ok(!existingFile.exists(), "exists.js doesn't exist anymore");
+});
diff --git a/dom/file/tests/test_file_from_blob.html b/dom/file/tests/test_file_from_blob.html
new file mode 100644
index 0000000000..8c12a2823a
--- /dev/null
+++ b/dom/file/tests/test_file_from_blob.html
@@ -0,0 +1,110 @@
+<!doctype html>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=819900
+-->
+    <head>
+<title>Test for crash caused by unloading and reloading srcdoc iframes</title>
+<script src="/tests/SimpleTest/SimpleTest.js"></script>
+<link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=819900">Mozilla Bug 819900</a>
+
+<pre id="test">
+<script>
+
+  var b = new Blob(['1234567890']);
+  ok(b, 'Blob created');
+  is(b.size, 10, 'Blob has the right size');
+
+  var status = false;
+  try {
+    f = new File(b);
+  } catch(e) {
+    status = true;
+  }
+  ok(status, "File throws if the second argument is missing");
+
+  status = false;
+  try {
+    f = new File(42, 'foobar.txt');
+  } catch(e) {
+    status = true;
+  }
+  ok(status, "File throws if the argument is not an array");
+
+  status = false;
+  try {
+    f = new File({}, 'foobar.txt');
+  } catch(e) {
+    status = true;
+  }
+  ok(status, "File throws if the argument is not an array");
+
+  status = false;
+  try {
+    f = new File("hello world", 'foobar.txt');
+  } catch(e) {
+    status = true;
+  }
+  ok(status, "File throws if the argument is not an array");
+
+  f = new File(['1234567890'], '');
+  ok(f, 'File created');
+  is(f.size, 10, 'File has the right size');
+  is(f.name, '');
+  is(f.type, '');
+
+  f = new File(['1234567890'], 42);
+  ok(f, 'File created');
+  is(f.size, 10, 'File has the right size');
+  is(f.name, '42');
+  is(f.type, '');
+
+  f = new File(['1234567890'], 'text.txt');
+  ok(f, 'File created');
+  is(f.size, 10, 'File has the right size');
+  is(f.name, 'text.txt');
+  is(f.type, '');
+
+  f = new File(['1234567890'], 'text.txt', { type: 'plain/text' });
+  ok(f, 'File created');
+  is(f.size, 10, 'File has the right size');
+  is(f.name, 'text.txt');
+  is(f.type, 'plain/text');
+
+  f = new File([b], 'text.txt');
+  ok(f, 'File created');
+  is(f.name, 'text.txt');
+  is(f.type, '');
+  is(f.size, b.size);
+
+  f = new File([b], 'test.txt', { type: 'plain/text' });
+  ok(f, 'File created');
+  is(f.name, 'test.txt');
+  is(f.type, 'plain/text');
+  is(f.size, b.size);
+
+  f = new File([b, b], 'test.txt', { type: 'plain/text' });
+  ok(f, 'File created');
+  is(f.name, 'test.txt');
+  is(f.type, 'plain/text');
+  is(f.size, b.size * 2);
+
+  var f2 = new File([f, f], 'test.txt', { type: 'plain/text' });
+  ok(f2, 'File created');
+  is(f2.name, 'test.txt');
+  is(f2.type, 'plain/text');
+  is(f2.size, f.size * 2);
+
+  var f2 = new File([f, f], 'test.txt', b);
+  ok(f2, 'File created');
+  is(f2.name, 'test.txt');
+  is(f2.type, b.type);
+  is(f2.size, f.size * 2);
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/file/tests/test_file_negative_date.html b/dom/file/tests/test_file_negative_date.html
new file mode 100644
index 0000000000..2e8528b88d
--- /dev/null
+++ b/dom/file/tests/test_file_negative_date.html
@@ -0,0 +1,29 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1158437
+-->
+<head>
+  <title>Test for negative date in File (Bug 1158437)</title>
+  <script type="text/javascript" src="/MochiKit/MochiKit.js"></script>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1158437">Mozilla Bug 1158437</a>
+
+<script class="testbody" type="text/javascript">
+"use strict";
+
+var blob = new Blob(['hello world']);
+var f1 = new File([blob], 'f1.txt', { lastModified: 0 });
+var f2 = new File([blob], 'f2.txt', { lastModified: -1 });
+var f3 = new File([blob], 'f3.txt', { lastModified: -1000 });
+
+is(f1.lastModified, 0, "lastModified == 0 is supported");
+is(f2.lastModified, -1, "lastModified == -1 is supported");
+is(f3.lastModified, -1000, "lastModified == -1000 is supported");
+
+</script>
+</body>
+</html>
diff --git a/dom/file/tests/test_fileapi_basic.html b/dom/file/tests/test_fileapi_basic.html
new file mode 100644
index 0000000000..7f7aed788e
--- /dev/null
+++ b/dom/file/tests/test_fileapi_basic.html
@@ -0,0 +1,24 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for FileReader API</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+  <script type="text/javascript" src="common_fileReader.js"></script>
+</head>
+
+<body>
+<script class="testbody" type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestLongerTimeout(3);
+
+test_setup()
+.then(data => {
+  return runBasicTests(data);
+})
+.then(SimpleTest.finish);
+
+</script>
+</body>
+</html>
diff --git a/dom/file/tests/test_fileapi_basic_worker.html b/dom/file/tests/test_fileapi_basic_worker.html
new file mode 100644
index 0000000000..03db1b4cb6
--- /dev/null
+++ b/dom/file/tests/test_fileapi_basic_worker.html
@@ -0,0 +1,38 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for FileReader API in workers</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+  <script type="text/javascript" src="common_fileReader.js"></script>
+</head>
+
+<body>
+<script class="testbody" type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestLongerTimeout(3);
+
+test_setup()
+.then(data => {
+  let worker = new Worker('worker_fileReader.js');
+  worker.postMessage({ tests: 'basic', data });
+
+  worker.onmessage = event => {
+    if (event.data.type == 'finish') {
+      SimpleTest.finish();
+      return;
+    }
+
+    if (event.data.type == 'check') {
+      ok(event.data.status, event.data.msg);
+      return;
+    }
+
+    ok(false, "Unknown message.");
+  }
+});
+
+</script>
+</body>
+</html>
diff --git a/dom/file/tests/test_fileapi_encoding.html b/dom/file/tests/test_fileapi_encoding.html
new file mode 100644
index 0000000000..f20a46ac6c
--- /dev/null
+++ b/dom/file/tests/test_fileapi_encoding.html
@@ -0,0 +1,24 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for FileReader API</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+  <script type="text/javascript" src="common_fileReader.js"></script>
+</head>
+
+<body>
+<script class="testbody" type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestLongerTimeout(3);
+
+test_setup()
+.then(data => {
+  return runEncodingTests(data);
+})
+.then(SimpleTest.finish);
+
+</script>
+</body>
+</html>
diff --git a/dom/file/tests/test_fileapi_encoding_worker.html b/dom/file/tests/test_fileapi_encoding_worker.html
new file mode 100644
index 0000000000..ab6827f086
--- /dev/null
+++ b/dom/file/tests/test_fileapi_encoding_worker.html
@@ -0,0 +1,38 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for FileReader API in workers</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+  <script type="text/javascript" src="common_fileReader.js"></script>
+</head>
+
+<body>
+<script class="testbody" type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestLongerTimeout(3);
+
+test_setup()
+.then(data => {
+  let worker = new Worker('worker_fileReader.js');
+  worker.postMessage({ tests: 'encoding', data });
+
+  worker.onmessage = event => {
+    if (event.data.type == 'finish') {
+      SimpleTest.finish();
+      return;
+    }
+
+    if (event.data.type == 'check') {
+      ok(event.data.status, event.data.msg);
+      return;
+    }
+
+    ok(false, "Unknown message.");
+  }
+});
+
+</script>
+</body>
+</html>
diff --git a/dom/file/tests/test_fileapi_other.html b/dom/file/tests/test_fileapi_other.html
new file mode 100644
index 0000000000..6c01415be8
--- /dev/null
+++ b/dom/file/tests/test_fileapi_other.html
@@ -0,0 +1,24 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for FileReader API</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+  <script type="text/javascript" src="common_fileReader.js"></script>
+</head>
+
+<body>
+<script class="testbody" type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestLongerTimeout(3);
+
+test_setup()
+.then(data => {
+  return runOtherTests(data);
+})
+.then(SimpleTest.finish);
+
+</script>
+</body>
+</html>
diff --git a/dom/file/tests/test_fileapi_other_worker.html b/dom/file/tests/test_fileapi_other_worker.html
new file mode 100644
index 0000000000..a535d3fcb4
--- /dev/null
+++ b/dom/file/tests/test_fileapi_other_worker.html
@@ -0,0 +1,38 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for FileReader API in workers</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+  <script type="text/javascript" src="common_fileReader.js"></script>
+</head>
+
+<body>
+<script class="testbody" type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestLongerTimeout(3);
+
+test_setup()
+.then(data => {
+  let worker = new Worker('worker_fileReader.js');
+  worker.postMessage({ tests: 'other', data });
+
+  worker.onmessage = event => {
+    if (event.data.type == 'finish') {
+      SimpleTest.finish();
+      return;
+    }
+
+    if (event.data.type == 'check') {
+      ok(event.data.status, event.data.msg);
+      return;
+    }
+
+    ok(false, "Unknown message.");
+  }
+});
+
+</script>
+</body>
+</html>
diff --git a/dom/file/tests/test_fileapi_slice_image.html b/dom/file/tests/test_fileapi_slice_image.html
new file mode 100644
index 0000000000..c873afa438
--- /dev/null
+++ b/dom/file/tests/test_fileapi_slice_image.html
@@ -0,0 +1,139 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for File API + Slice</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="common_blob.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+
+<body>
+
+<p id="display">
+  <canvas id=canvas width=1100 height=1100 hidden moz-opaque></canvas>
+  <canvas id=testcanvas hidden moz-opaque></canvas>
+</p>
+
+<script type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestLongerTimeout(4);
+
+// Create files containing data we'll test with. We'll want long
+// strings to ensure they span multiple buffers while loading
+
+let canvasData;
+let testBinaryData;
+
+function imageLoadHandler(event, resolve) {
+  let origcanvas = $("canvas");
+  let testcanvas = $("testcanvas");
+  let image = event.target;
+  is(image.naturalWidth, origcanvas.width, "width correct");
+  is(image.naturalHeight, origcanvas.height, "height correct");
+
+  testcanvas.width = origcanvas.width;
+  testcanvas.height = origcanvas.height;
+  testcanvas.getContext("2d").drawImage(image, 0, 0);
+  // Do not use |is(testcanvas.toDataURL("image/png"), origcanvas.toDataURL("image/png"), "...");| that results in a _very_ long line.
+  let origDataURL = origcanvas.toDataURL("image/png");
+  let testDataURL = testcanvas.toDataURL("image/png");
+  is(testDataURL.length, origDataURL.length,
+     "Length of correct image data");
+  ok(testDataURL == origDataURL,
+     "Content of correct image data");
+  resolve();
+}
+
+createCanvasURL()
+.then(data => {
+  for (var i = 0; i < 256; i++) {
+    testBinaryData += String.fromCharCode(i);
+  }
+  while (testBinaryData.length < 20000) {
+    testBinaryData += testBinaryData;
+  }
+
+  canvasData = data;
+})
+
+// image in the middle
+.then(() => {
+  return createFile(testBinaryData + canvasData + testBinaryData, "middleTestFile");
+})
+
+// image in the middle - loader
+.then(file => {
+  return new Promise(resolve => {
+    is(file.size, canvasData.length + testBinaryData.length * 2, "correct file size (middle)");
+
+    var img = new Image();
+    img.src = URL.createObjectURL(file.slice(testBinaryData.length,
+                                             testBinaryData.length + canvasData.length));
+    img.onload = event => {
+      imageLoadHandler(event, resolve);
+    }
+  });
+})
+
+// image at start
+.then(() => {
+  return createFile(canvasData + testBinaryData, "startTestFile");
+})
+
+// image at start - loader
+.then(file => {
+  return new Promise(resolve => {
+    is(file.size, canvasData.length + testBinaryData.length, "correct file size (start)");
+
+    var img = new Image();
+    img.src = URL.createObjectURL(file.slice(0, canvasData.length));
+    img.onload = event => {
+      imageLoadHandler(event, resolve);
+    }
+  });
+})
+
+// image at end
+.then(() => {
+  return createFile(testBinaryData + canvasData, "endTestFile");
+})
+
+// image at end - loader
+.then(file => {
+  return new Promise(resolve => {
+    is(file.size, canvasData.length + testBinaryData.length, "correct file size (end)");
+
+    var img = new Image();
+    img.src = URL.createObjectURL(file.slice(testBinaryData.length,
+                                             testBinaryData.length + canvasData.length));
+    img.onload = event => {
+      imageLoadHandler(event, resolve);
+    }
+  });
+})
+
+// image past end
+.then(() => {
+  return createFile(testBinaryData + canvasData, "pastEndTestFile");
+})
+
+// image past end - loader
+.then(file => {
+  return new Promise(resolve => {
+    is(file.size, canvasData.length + testBinaryData.length, "correct file size (end)");
+
+    var img = new Image();
+    img.src = URL.createObjectURL(file.slice(testBinaryData.length,
+                                             testBinaryData.length + canvasData.length + 1000));
+    img.onload = event => {
+      imageLoadHandler(event, resolve);
+    }
+  });
+})
+
+.then(SimpleTest.finish);
+
+</script>
+</body>
+</html>
diff --git a/dom/file/tests/test_fileapi_slice_memFile_1.html b/dom/file/tests/test_fileapi_slice_memFile_1.html
new file mode 100644
index 0000000000..56d63d15ba
--- /dev/null
+++ b/dom/file/tests/test_fileapi_slice_memFile_1.html
@@ -0,0 +1,37 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for File API + Slice (in memory)</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="common_blob.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+
+<body>
+
+<p id="display">
+  <canvas id=canvas width=1100 height=1100 hidden moz-opaque></canvas>
+</p>
+
+<script type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestLongerTimeout(4);
+
+createCanvasURL()
+.then(data => {
+  let cx = $("canvas").getContext('2d');
+  return Promise.all([toBlobPromise(cx.canvas),
+                      Promise.resolve(data)]);
+})
+
+.then(args => {
+  let [memFile, data] = args;
+  return testSlice(memFile, data.length, "image/png", data, "memFile", RANGE_1);
+})
+
+.then(SimpleTest.finish);
+
+</script>
+</body>
+</html>
diff --git a/dom/file/tests/test_fileapi_slice_memFile_2.html b/dom/file/tests/test_fileapi_slice_memFile_2.html
new file mode 100644
index 0000000000..aef8813bf5
--- /dev/null
+++ b/dom/file/tests/test_fileapi_slice_memFile_2.html
@@ -0,0 +1,37 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for File API + Slice (in memory)</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="common_blob.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+
+<body>
+
+<p id="display">
+  <canvas id=canvas width=1100 height=1100 hidden moz-opaque></canvas>
+</p>
+
+<script type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestLongerTimeout(4);
+
+createCanvasURL()
+.then(data => {
+  let cx = $("canvas").getContext('2d');
+  return Promise.all([toBlobPromise(cx.canvas),
+                      Promise.resolve(data)]);
+})
+
+.then(args => {
+  let [memFile, data] = args;
+  return testSlice(memFile, data.length, "image/png", data, "memFile", RANGE_2);
+})
+
+.then(SimpleTest.finish);
+
+</script>
+</body>
+</html>
diff --git a/dom/file/tests/test_fileapi_slice_realFile_1.html b/dom/file/tests/test_fileapi_slice_realFile_1.html
new file mode 100644
index 0000000000..97798d805a
--- /dev/null
+++ b/dom/file/tests/test_fileapi_slice_realFile_1.html
@@ -0,0 +1,37 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for File API + Slice (in file)</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="common_blob.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+
+<body>
+
+<p id="display">
+  <canvas id=canvas width=1100 height=1100 hidden moz-opaque></canvas>
+</p>
+
+<script type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestLongerTimeout(4);
+
+let canvasData;
+
+createCanvasURL()
+.then(data => {
+  canvasData = data;
+  return createFile(data, "basicTestFile1");
+})
+
+.then(file => {
+  return testSlice(file, canvasData.length, "", canvasData, "fileFile", RANGE_1);
+})
+
+.then(SimpleTest.finish);
+
+</script>
+</body>
+</html>
diff --git a/dom/file/tests/test_fileapi_slice_realFile_2.html b/dom/file/tests/test_fileapi_slice_realFile_2.html
new file mode 100644
index 0000000000..882ce61c03
--- /dev/null
+++ b/dom/file/tests/test_fileapi_slice_realFile_2.html
@@ -0,0 +1,37 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for File API + Slice (in file)</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="common_blob.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+
+<body>
+
+<p id="display">
+  <canvas id=canvas width=1100 height=1100 hidden moz-opaque></canvas>
+</p>
+
+<script type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestLongerTimeout(4);
+
+let canvasData;
+
+createCanvasURL()
+.then(data => {
+  canvasData = data;
+  return createFile(data, "basicTestFile2");
+})
+
+.then(file => {
+  return testSlice(file, canvasData.length, "", canvasData, "fileFile", RANGE_2);
+})
+
+.then(SimpleTest.finish);
+
+</script>
+</body>
+</html>
diff --git a/dom/file/tests/test_fileapi_twice.html b/dom/file/tests/test_fileapi_twice.html
new file mode 100644
index 0000000000..96e7febdce
--- /dev/null
+++ b/dom/file/tests/test_fileapi_twice.html
@@ -0,0 +1,24 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for FileReader API</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+  <script type="text/javascript" src="common_fileReader.js"></script>
+</head>
+
+<body>
+<script class="testbody" type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestLongerTimeout(3);
+
+test_setup()
+.then(data => {
+  return runTwiceTests(data);
+})
+.then(SimpleTest.finish);
+
+</script>
+</body>
+</html>
diff --git a/dom/file/tests/test_fileapi_twice_worker.html b/dom/file/tests/test_fileapi_twice_worker.html
new file mode 100644
index 0000000000..a79d3992b2
--- /dev/null
+++ b/dom/file/tests/test_fileapi_twice_worker.html
@@ -0,0 +1,38 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for FileReader API in workers</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+  <script type="text/javascript" src="common_fileReader.js"></script>
+</head>
+
+<body>
+<script class="testbody" type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.requestLongerTimeout(3);
+
+test_setup()
+.then(data => {
+  let worker = new Worker('worker_fileReader.js');
+  worker.postMessage({ tests: 'twice', data });
+
+  worker.onmessage = event => {
+    if (event.data.type == 'finish') {
+      SimpleTest.finish();
+      return;
+    }
+
+    if (event.data.type == 'check') {
+      ok(event.data.status, event.data.msg);
+      return;
+    }
+
+    ok(false, "Unknown message.");
+  }
+});
+
+</script>
+</body>
+</html>
diff --git a/dom/file/tests/test_ipc_messagemanager_blob.js b/dom/file/tests/test_ipc_messagemanager_blob.js
new file mode 100644
index 0000000000..c9d2a914f6
--- /dev/null
+++ b/dom/file/tests/test_ipc_messagemanager_blob.js
@@ -0,0 +1,102 @@
+"use strict";
+
+const { XPCShellContentUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/XPCShellContentUtils.sys.mjs"
+);
+
+XPCShellContentUtils.init(this);
+
+function childFrameScript() {
+  addMessageListener("test:ipcClonedMessage", function(message) {
+    if (!Blob.isInstance(message.json)) {
+      sendAsyncMessage(message.name, message.json);
+      return;
+    }
+
+    let reader = new FileReader();
+    reader.addEventListener("load", function() {
+      let response =
+        reader.result == "this is a great success!" ? message.json : "error";
+      sendAsyncMessage(message.name, response);
+    });
+    reader.readAsText(message.json);
+  });
+}
+
+add_task(async function test() {
+  let page = await XPCShellContentUtils.loadContentPage("about:blank", {
+    remote: true,
+  });
+
+  page.loadFrameScript(childFrameScript);
+
+  const blobString = "this is a great success!";
+
+  const messages = [
+    "hi!",
+    "",
+    2,
+    -0.04,
+    34329873249872400000000000000,
+    true,
+    false,
+    null,
+    0,
+
+    // Make sure this one is always last.
+    new Blob(["this ", "is ", "a ", "great ", "success!"], {
+      type: "text/plain",
+    }),
+  ];
+  let receivedMessageIndex = 0;
+
+  let mm = page.browser.messageManager;
+  let done = new Promise(resolve => {
+    mm.addMessageListener("test:ipcClonedMessage", async message => {
+      let data = message.json;
+
+      if (Blob.isInstance(data)) {
+        equal(receivedMessageIndex, messages.length - 1, "Blob is last");
+        equal(
+          data.size,
+          messages[receivedMessageIndex].size,
+          "Correct blob size"
+        );
+        equal(
+          data.type,
+          messages[receivedMessageIndex].type,
+          "Correct blob type"
+        );
+
+        let reader1 = new FileReader();
+        reader1.readAsText(data);
+
+        let reader2 = new FileReader();
+        reader2.readAsText(messages[receivedMessageIndex]);
+
+        await Promise.all([
+          new Promise(res => (reader1.onload = res)),
+          new Promise(res => (reader2.onload = res)),
+        ]);
+
+        equal(reader1.result, blobString, "Result 1");
+        equal(reader2.result, blobString, "Result 2");
+
+        resolve();
+      } else {
+        equal(
+          data,
+          messages[receivedMessageIndex++],
+          "Got correct round-tripped response"
+        );
+      }
+    });
+  });
+
+  for (let message of messages) {
+    mm.sendAsyncMessage("test:ipcClonedMessage", message);
+  }
+
+  await done;
+  await page.close();
+});
diff --git a/dom/file/tests/test_mozfiledataurl.html b/dom/file/tests/test_mozfiledataurl.html
new file mode 100644
index 0000000000..68c88fa28c
--- /dev/null
+++ b/dom/file/tests/test_mozfiledataurl.html
@@ -0,0 +1,224 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=utf-8">
+  <title>Test for File urls</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body onload="start()">
+<p id="display">
+<iframe id=inner></iframe>
+<iframe id=iframe></iframe>
+<img id=img onload="gen.next(event);">
+<audio id=audio onloadeddata="gen.next(event);">
+</p>
+<div id="content" style="display: none">
+
+</div>
+<pre id="test">
+<script class="testbody" type="application/javascript">
+
+try {
+  URL.createObjectURL(undefined);
+} catch(e) { }
+
+window.addEventListener("message", function(e) {
+  gen.next(JSON.parse(e.data));
+});
+
+const innerSameSiteURI = "file_mozfiledataurl_inner.html";
+const innerCrossSiteURI = "http://example.com/tests/dom/file/tests/file_mozfiledataurl_inner.html"
+
+var fileNames = ["file_mozfiledataurl_img.jpg",
+                 "file_mozfiledataurl_audio.ogg",
+                 "file_mozfiledataurl_doc.html",
+                 "file_mozfiledataurl_text.txt"];
+
+function start() {
+  let xhr = new XMLHttpRequest;
+  xhr.open("GET", "/dynamic/getMyDirectory.sjs", false);
+  xhr.send();
+  let basePath = xhr.responseText;
+
+  let fullFileNames = [];
+  for (let name of fileNames) {
+    fullFileNames.push(basePath + name);
+  }
+
+  var script = SpecialPowers.loadChromeScript(SimpleTest.getTestFileURL("create_file_objects.js"));
+
+  script.addMessageListener("created-file-objects", function handler(files) {
+    script.removeMessageListener("created-file-objects", handler);
+    gen = runTest(files);
+    gen.next();
+  });
+
+  script.sendAsyncMessage("create-file-objects", {fileNames: fullFileNames});
+};
+
+SimpleTest.waitForExplicitFinish();
+SimpleTest.expectAssertions(0, 3);
+
+function* runTest([imgFile, audioFile, docFile, xhrFile]) {
+  inner = document.getElementById('inner');
+  img = document.getElementById('img');
+  audio = document.getElementById('audio');
+  iframe = document.getElementById('iframe');
+  inner.onload = function() { gen.next("inner loaded"); };
+
+  // Attempt to load a image in this document
+  var fileurl = URL.createObjectURL(imgFile);
+  img.src = fileurl;
+  var e = (yield);
+  is(e.type, "load", "loaded successfully");
+  is(img.width, 120, "correct width");
+  is(img.height, 90, "correct height");
+
+  // Revoke url and attempt to load a image in this document
+  img.src = "file_mozfiledataurl_img.jpg";
+  is((yield).type, "load", "successfull reset image");
+  URL.revokeObjectURL(fileurl);
+  todo(false, "urls need to act like 404s, not fail to parse");
+/*  img.src = fileurl;
+  var e = (yield);
+  is(e.type, "error", "failed successfully");
+  isnot(img.width, 120, "correct error width");
+  isnot(img.height, 90, "correct error height");
+*/
+  // Generate new fileurl and make sure it's different from the old
+  var oldFileurl = fileurl;
+  fileurl = URL.createObjectURL(imgFile);
+  isnot(fileurl, oldFileurl, "URL.createObjectURL generated the same url twice");
+
+  // Attempt to load an image in a different same-origin document
+  inner.src = innerSameSiteURI;
+  yield undefined;
+  inner.contentWindow.postMessage(JSON.stringify({img:fileurl}), "*");
+  var res = (yield);
+  is(res.type, "load", "loaded successfully");
+  is(res.width, 120, "correct width");
+  is(res.height, 90, "correct height");
+
+  // Attempt to load an image in a different cross-origin document
+  inner.src = innerCrossSiteURI;
+  yield undefined;
+  inner.contentWindow.postMessage(JSON.stringify({img:fileurl}), "*");
+  var res = (yield);
+  is(res.type, "error", "failed successfully");
+  isnot(res.width, 120, "correct error width");
+  isnot(res.height, 90, "correct error height");
+
+  // Attempt to load an audio in this document
+  fileurl = URL.createObjectURL(audioFile);
+  audio.src = fileurl;
+  var e = (yield);
+  is(e.type, "loadeddata", "loaded successfully");
+
+  // Revoke url and attempt to load a audio in this document
+  audio.src = "file_mozfiledataurl_audio.ogg";
+  is((yield).type, "loadeddata", "successfully reset audio");
+  URL.revokeObjectURL(fileurl);
+  todo(false, "urls need to act like 404s, not fail to parse");
+/*  img.src = fileurl;
+  var e = (yield);
+  is(e.type, "error", "failed successfully");
+  isnot(img.width, 120, "correct error width");
+  isnot(img.height, 90, "correct error height");
+*/
+  // Generate new fileurl and make sure it's different from the old
+  var oldFileurl = fileurl;
+  fileurl = URL.createObjectURL(audioFile);
+  isnot(fileurl, oldFileurl, "URL.createObjectURL generated the same url twice");
+
+  // Attempt to load an audio in a different same-origin document
+  inner.src = innerSameSiteURI;
+  yield undefined;
+  inner.contentWindow.postMessage(JSON.stringify({audio:fileurl}), "*");
+  var res = (yield);
+  is(res.type, "loadeddata", "loaded successfully");
+
+  // Attempt to load an audio in a different cross-origin document
+  inner.src = innerCrossSiteURI;
+  yield undefined;
+  inner.contentWindow.postMessage(JSON.stringify({audio:fileurl}), "*");
+  var res = (yield);
+  is(res.type, "error", "failed successfully");
+
+  // Attempt to load a HTML document in an iframe in this document
+  iframe.onload = function() { gen.next(); };
+  iframe.src = "file_mozfiledataurl_doc.html";
+  yield undefined;
+  is(iframe.contentDocument.getElementsByTagName("p")[0].textContent,
+     "This here is a document!",
+     "iframe loaded successfully");
+  is(iframe.contentDocument.getElementById("img").width, 120,
+     "image in iframe width");
+  is(iframe.contentDocument.getElementById("img").height, 90,
+     "image in iframe height");
+
+  // Attempt to load a HTML document in an iframe in this document, using file url
+  fileurl = URL.createObjectURL(docFile);
+  iframe.src = fileurl;
+  yield undefined;
+  is(iframe.contentDocument.getElementsByTagName("p")[0].textContent,
+     "This here is a document!",
+     "iframe loaded successfully");
+  isnot(iframe.contentDocument.getElementById("img").width, 120,
+        "failed image in iframe width");
+  isnot(iframe.contentDocument.getElementById("img").height, 90,
+        "failed image in iframe height");
+
+  // Attempt to load a HTML document in an iframe in inner document
+  inner.src = innerSameSiteURI;
+  is((yield), "inner loaded", "correct gen.next()");
+  inner.contentWindow.postMessage(JSON.stringify({iframe:"file_mozfiledataurl_doc.html"}), "*");
+  var res = (yield);
+  is(res.type, "load", "loaded successfully");
+  is(res.text, "This here is a document!", "loaded successfully");
+  is(res.imgWidth, 120, "correct width");
+
+  // Attempt to load a HTML document in an iframe in inner document, using file url
+  inner.contentWindow.postMessage(JSON.stringify({iframe:fileurl}), "*");
+  var res = (yield);
+  is(res.type, "load", "loaded successfully");
+  is(res.text, "This here is a document!", "loaded successfully");
+  isnot(res.imgWidth, 120, "correct width");
+
+  // Attempt to load a HTML document in an iframe in inner cross-site document, using file url
+  inner.src = innerCrossSiteURI;
+  is((yield), "inner loaded", "correct gen.next()");
+  inner.contentWindow.postMessage(JSON.stringify({iframe:fileurl}), "*");
+  var res = (yield);
+  is(res.type, "error", "load failed successfully");
+
+  // Attempt to load file url using XHR
+  fileurl = URL.createObjectURL(xhrFile);
+  xhr = new XMLHttpRequest;
+  xhr.onload = function() { gen.next("XHR finished"); };
+  xhr.open("GET", fileurl);
+  xhr.send();
+  is((yield), "XHR finished", "correct gen.next()");
+  xhr.responseText == "Yarr, here be plaintext file, ya landlubber\n";
+
+  // Attempt to load file url using XHR in inner document
+  inner.src = innerSameSiteURI;
+  is((yield), "inner loaded", "correct gen.next()");
+  inner.contentWindow.postMessage(JSON.stringify({xhr:fileurl}), "*");
+  var res = (yield);
+  is(res.didThrow, undefined, "load successful");
+  is(res.text, "Yarr, here be plaintext file, ya landlubber\n", "load successful");
+
+  // Attempt to load file url using XHR
+  inner.src = innerCrossSiteURI;
+  is((yield), "inner loaded", "correct gen.next()");
+  inner.contentWindow.postMessage(JSON.stringify({xhr:fileurl}), "*");
+  var res = (yield);
+  is(res.didError, true, "load failed successfully");
+
+  SimpleTest.finish();
+}
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/file/tests/test_nonascii_blob_url.html b/dom/file/tests/test_nonascii_blob_url.html
new file mode 100644
index 0000000000..1c6c833958
--- /dev/null
+++ b/dom/file/tests/test_nonascii_blob_url.html
@@ -0,0 +1,28 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test blob URL for non-ascii domain</title>
+  <script type="text/javascript" src="/MochiKit/MochiKit.js"></script>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<div id="content"></div>
+<script class="testbody" type="text/javascript">
+
+var iframe = document.createElement('iframe');
+iframe.src = 'http://xn--exmple-cua.test/tests/dom/file/tests/file_nonascii_blob_url.html';
+iframe.onload = function() {
+  iframe.contentWindow.postMessage('hello world', '*');
+  onmessage = function(e) {
+    is(e.data, 'hello world', "Blob URL for non-ascii domain works");
+    SimpleTest.finish();
+  }
+}
+
+document.getElementById('content').appendChild(iframe);
+SimpleTest.waitForExplicitFinish();
+
+</script>
+</body>
+</html>
diff --git a/dom/file/tests/worker_blob_reading.js b/dom/file/tests/worker_blob_reading.js
new file mode 100644
index 0000000000..4dc3030719
--- /dev/null
+++ b/dom/file/tests/worker_blob_reading.js
@@ -0,0 +1,26 @@
+importScripts("common_blob_reading.js");
+
+function info(message) {
+  postMessage({ type: "info", message });
+}
+
+function ok(a, message) {
+  postMessage({ type: "test", test: !!a, message });
+}
+
+function is(a, b, message) {
+  ok(a === b, message);
+}
+
+onmessage = function(e) {
+  self[e.data.func](e.data.blob, e.data.content).then(
+    () => {
+      postMessage({ type: "done" });
+    },
+    exc => {
+      dump(exc);
+      dump(exc.stack);
+      postMessage({ type: "error", message: exc.toString() });
+    }
+  );
+};
diff --git a/dom/file/tests/worker_bug1507893.js b/dom/file/tests/worker_bug1507893.js
new file mode 100644
index 0000000000..06fce2b2ef
--- /dev/null
+++ b/dom/file/tests/worker_bug1507893.js
@@ -0,0 +1,5 @@
+onmessage = e => {
+  fetch(e.data)
+    .then(r => r.blob())
+    .then(blob => postMessage(blob));
+};
diff --git a/dom/file/tests/worker_bug1742540.js b/dom/file/tests/worker_bug1742540.js
new file mode 100644
index 0000000000..c0330ccb56
--- /dev/null
+++ b/dom/file/tests/worker_bug1742540.js
@@ -0,0 +1,5 @@
+onmessage = e => {
+  let file = e.data.file;
+  let port = e.data.port;
+  port.postMessage(e.data.message);
+};
diff --git a/dom/file/tests/worker_fileReader.js b/dom/file/tests/worker_fileReader.js
new file mode 100644
index 0000000000..2e8408d1bb
--- /dev/null
+++ b/dom/file/tests/worker_fileReader.js
@@ -0,0 +1,30 @@
+importScripts("common_fileReader.js");
+
+function ok(a, msg) {
+  postMessage({ type: "check", msg, status: !!a });
+}
+
+function is(a, b, msg) {
+  ok(a === b, msg);
+}
+
+onmessage = event => {
+  let p;
+
+  if (event.data.tests == "basic") {
+    p = runBasicTests(event.data.data);
+  } else if (event.data.tests == "encoding") {
+    p = runEncodingTests(event.data.data);
+  } else if (event.data.tests == "twice") {
+    p = runTwiceTests(event.data.data);
+  } else if (event.data.tests == "other") {
+    p = runOtherTests(event.data.data);
+  } else {
+    postMessage({ type: "error" });
+    return;
+  }
+
+  p.then(() => {
+    postMessage({ type: "finish" });
+  });
+};
diff --git a/dom/file/tests/xpcshell.ini b/dom/file/tests/xpcshell.ini
new file mode 100644
index 0000000000..2f817948d3
--- /dev/null
+++ b/dom/file/tests/xpcshell.ini
@@ -0,0 +1,8 @@
+[DEFAULT]
+
+[test_bloburi.js]
+[test_createFile.js]
+[test_ipc_messagemanager_blob.js]
+skip-if = os == "android"
+[test_agentcluster_bloburl.js]
+skip-if = os == "android"
diff --git a/dom/file/uri/BlobURL.cpp b/dom/file/uri/BlobURL.cpp
new file mode 100644
index 0000000000..b3afd60437
--- /dev/null
+++ b/dom/file/uri/BlobURL.cpp
@@ -0,0 +1,171 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsIClassInfoImpl.h"
+#include "nsIObjectInputStream.h"
+#include "nsIObjectOutputStream.h"
+
+#include "mozilla/dom/BlobURL.h"
+#include "mozilla/dom/BlobURLProtocolHandler.h"
+#include "mozilla/ipc/BackgroundUtils.h"
+#include "mozilla/ipc/URIUtils.h"
+
+using namespace mozilla::dom;
+
+static NS_DEFINE_CID(kThisSimpleURIImplementationCID,
+                     NS_THIS_SIMPLEURI_IMPLEMENTATION_CID);
+
+NS_IMPL_ADDREF_INHERITED(BlobURL, mozilla::net::nsSimpleURI)
+NS_IMPL_RELEASE_INHERITED(BlobURL, mozilla::net::nsSimpleURI)
+
+NS_IMPL_CLASSINFO(BlobURL, nullptr, nsIClassInfo::THREADSAFE,
+                  NS_HOSTOBJECTURI_CID);
+// Empty CI getter. We only need nsIClassInfo for Serialization
+NS_IMPL_CI_INTERFACE_GETTER0(BlobURL)
+
+NS_INTERFACE_MAP_BEGIN(BlobURL)
+  if (aIID.Equals(kHOSTOBJECTURICID))
+    foundInterface = static_cast<nsIURI*>(this);
+  else if (aIID.Equals(kThisSimpleURIImplementationCID)) {
+    // Need to return explicitly here, because if we just set foundInterface
+    // to null the NS_INTERFACE_MAP_END_INHERITING will end up calling into
+    // nsSimplURI::QueryInterface and finding something for this CID.
+    *aInstancePtr = nullptr;
+    return NS_NOINTERFACE;
+  } else
+    NS_IMPL_QUERY_CLASSINFO(BlobURL)
+NS_INTERFACE_MAP_END_INHERITING(mozilla::net::nsSimpleURI)
+
+BlobURL::BlobURL() : mRevoked(false) {}
+
+// nsISerializable methods:
+
+NS_IMETHODIMP
+BlobURL::Read(nsIObjectInputStream* aStream) {
+  MOZ_ASSERT_UNREACHABLE("Use nsIURIMutator.read() instead");
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+nsresult BlobURL::ReadPrivate(nsIObjectInputStream* aStream) {
+  nsresult rv = mozilla::net::nsSimpleURI::ReadPrivate(aStream);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = aStream->ReadBoolean(&mRevoked);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BlobURL::Write(nsIObjectOutputStream* aStream) {
+  nsresult rv = mozilla::net::nsSimpleURI::Write(aStream);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = aStream->WriteBoolean(mRevoked);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP_(void)
+BlobURL::Serialize(mozilla::ipc::URIParams& aParams) {
+  using namespace mozilla::ipc;
+
+  HostObjectURIParams hostParams;
+  URIParams simpleParams;
+
+  mozilla::net::nsSimpleURI::Serialize(simpleParams);
+  hostParams.simpleParams() = simpleParams;
+
+  hostParams.revoked() = mRevoked;
+
+  aParams = hostParams;
+}
+
+bool BlobURL::Deserialize(const mozilla::ipc::URIParams& aParams) {
+  using namespace mozilla::ipc;
+
+  if (aParams.type() != URIParams::THostObjectURIParams) {
+    NS_ERROR("Received unknown parameters from the other process!");
+    return false;
+  }
+
+  const HostObjectURIParams& hostParams = aParams.get_HostObjectURIParams();
+
+  if (!mozilla::net::nsSimpleURI::Deserialize(hostParams.simpleParams())) {
+    return false;
+  }
+
+  mRevoked = hostParams.revoked();
+  return true;
+}
+
+nsresult BlobURL::SetScheme(const nsACString& aScheme) {
+  // Disallow setting the scheme, since that could cause us to be associated
+  // with a different protocol handler.
+  return NS_ERROR_FAILURE;
+}
+
+// nsIURI methods:
+nsresult BlobURL::CloneInternal(
+    mozilla::net::nsSimpleURI::RefHandlingEnum aRefHandlingMode,
+    const nsACString& newRef, nsIURI** aClone) {
+  nsCOMPtr<nsIURI> simpleClone;
+  nsresult rv = mozilla::net::nsSimpleURI::CloneInternal(
+      aRefHandlingMode, newRef, getter_AddRefs(simpleClone));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+#ifdef DEBUG
+  RefPtr<BlobURL> uriCheck;
+  rv = simpleClone->QueryInterface(kHOSTOBJECTURICID, getter_AddRefs(uriCheck));
+  MOZ_ASSERT(NS_SUCCEEDED(rv) && uriCheck);
+#endif
+
+  BlobURL* u = static_cast<BlobURL*>(simpleClone.get());
+  u->mRevoked = mRevoked;
+
+  simpleClone.forget(aClone);
+  return NS_OK;
+}
+
+/* virtual */
+nsresult BlobURL::EqualsInternal(
+    nsIURI* aOther, mozilla::net::nsSimpleURI::RefHandlingEnum aRefHandlingMode,
+    bool* aResult) {
+  if (!aOther) {
+    *aResult = false;
+    return NS_OK;
+  }
+
+  RefPtr<BlobURL> otherUri;
+  aOther->QueryInterface(kHOSTOBJECTURICID, getter_AddRefs(otherUri));
+  if (!otherUri) {
+    *aResult = false;
+    return NS_OK;
+  }
+
+  // Compare the member data that our base class knows about.
+  *aResult =
+      mozilla::net::nsSimpleURI::EqualsInternal(otherUri, aRefHandlingMode);
+
+  // We don't want to compare the revoked flag.
+  return NS_OK;
+}
+
+// Queries this list of interfaces. If none match, it queries mURI.
+NS_IMPL_NSIURIMUTATOR_ISUPPORTS(BlobURL::Mutator, nsIURISetters, nsIURIMutator,
+                                nsISerializable, nsIBlobURLMutator)
+
+NS_IMETHODIMP
+BlobURL::Mutate(nsIURIMutator** aMutator) {
+  RefPtr<BlobURL::Mutator> mutator = new BlobURL::Mutator();
+  nsresult rv = mutator->InitFromURI(this);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  mutator.forget(aMutator);
+  return NS_OK;
+}
diff --git a/dom/file/uri/BlobURL.h b/dom/file/uri/BlobURL.h
new file mode 100644
index 0000000000..1e7a91daa4
--- /dev/null
+++ b/dom/file/uri/BlobURL.h
@@ -0,0 +1,123 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_BlobURL_h
+#define mozilla_dom_BlobURL_h
+
+#include "nsCOMPtr.h"
+#include "nsISerializable.h"
+#include "nsSimpleURI.h"
+#include "prtime.h"
+
+#define NS_HOSTOBJECTURI_CID                         \
+  {                                                  \
+    0xf5475c51, 0x59a7, 0x4757, {                    \
+      0xb3, 0xd9, 0xe2, 0x11, 0xa9, 0x41, 0x08, 0x72 \
+    }                                                \
+  }
+
+#define NS_IBLOBURLMUTATOR_IID                       \
+  {                                                  \
+    0xf91e646d, 0xe87b, 0x485e, {                    \
+      0xbb, 0xc8, 0x0e, 0x8a, 0x2e, 0xe9, 0x87, 0xa9 \
+    }                                                \
+  }
+
+class NS_NO_VTABLE nsIBlobURLMutator : public nsISupports {
+ public:
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_IBLOBURLMUTATOR_IID)
+  NS_IMETHOD SetRevoked(bool aRevoked) = 0;
+};
+
+inline NS_DEFINE_CID(kHOSTOBJECTURICID, NS_HOSTOBJECTURI_CID);
+
+NS_DEFINE_STATIC_IID_ACCESSOR(nsIBlobURLMutator, NS_IBLOBURLMUTATOR_IID)
+
+namespace mozilla::dom {
+
+/**
+ * These URIs refer to host objects with "blob" scheme.
+ */
+class BlobURL final : public mozilla::net::nsSimpleURI {
+ private:
+  BlobURL();
+
+ public:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_NSISERIALIZABLE
+
+  // Override CloneInternal() and EqualsInternal()
+  nsresult CloneInternal(RefHandlingEnum aRefHandlingMode,
+                         const nsACString& newRef, nsIURI** aClone) override;
+  nsresult EqualsInternal(nsIURI* aOther, RefHandlingEnum aRefHandlingMode,
+                          bool* aResult) override;
+  NS_IMETHOD_(void) Serialize(mozilla::ipc::URIParams& aParams) override;
+
+  // Override StartClone to hand back a BlobURL
+  mozilla::net::nsSimpleURI* StartClone(RefHandlingEnum refHandlingMode,
+                                        const nsACString& newRef) override {
+    BlobURL* url = new BlobURL();
+    SetRefOnClone(url, refHandlingMode, newRef);
+    return url;
+  }
+
+  bool Revoked() const { return mRevoked; }
+
+  NS_IMETHOD Mutate(nsIURIMutator** _retval) override;
+
+ private:
+  ~BlobURL() override = default;
+
+  nsresult SetScheme(const nsACString& aProtocol) override;
+  bool Deserialize(const mozilla::ipc::URIParams&);
+  nsresult ReadPrivate(nsIObjectInputStream* stream);
+
+  bool mRevoked;
+
+ public:
+  class Mutator final : public nsIURIMutator,
+                        public BaseURIMutator<BlobURL>,
+                        public nsIBlobURLMutator,
+                        public nsISerializable {
+    NS_DECL_ISUPPORTS
+    NS_FORWARD_SAFE_NSIURISETTERS_RET(mURI)
+    NS_DEFINE_NSIMUTATOR_COMMON
+
+    NS_IMETHOD
+    Write(nsIObjectOutputStream* aOutputStream) override {
+      return NS_ERROR_NOT_IMPLEMENTED;
+    }
+
+    [[nodiscard]] NS_IMETHOD Read(nsIObjectInputStream* aStream) override {
+      return InitFromInputStream(aStream);
+    }
+
+    NS_IMETHOD SetRevoked(bool aRevoked) override {
+      mURI->mRevoked = aRevoked;
+      return NS_OK;
+    }
+
+    Mutator() = default;
+
+   private:
+    ~Mutator() = default;
+
+    friend class BlobURL;
+  };
+
+  friend BaseURIMutator<BlobURL>;
+};
+
+#define NS_HOSTOBJECTURIMUTATOR_CID                  \
+  {                                                  \
+    0xbbe50ef2, 0x80eb, 0x469d, {                    \
+      0xb7, 0x0d, 0x02, 0x85, 0x82, 0x75, 0x38, 0x9f \
+    }                                                \
+  }
+
+}  // namespace mozilla::dom
+
+#endif /* mozilla_dom_BlobURL_h */
diff --git a/dom/file/uri/BlobURLChannel.cpp b/dom/file/uri/BlobURLChannel.cpp
new file mode 100644
index 0000000000..6a7d4f1be6
--- /dev/null
+++ b/dom/file/uri/BlobURLChannel.cpp
@@ -0,0 +1,86 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "BlobURLChannel.h"
+#include "mozilla/dom/BlobImpl.h"
+#include "mozilla/dom/BlobURL.h"
+#include "mozilla/dom/BlobURLInputStream.h"
+
+using namespace mozilla::dom;
+
+BlobURLChannel::BlobURLChannel(nsIURI* aURI, nsILoadInfo* aLoadInfo)
+    : mContentStreamOpened(false) {
+  SetURI(aURI);
+  SetOriginalURI(aURI);
+  SetLoadInfo(aLoadInfo);
+
+  // If we're sandboxed, make sure to clear any owner the channel
+  // might already have.
+  if (aLoadInfo && aLoadInfo->GetLoadingSandboxed()) {
+    SetOwner(nullptr);
+  }
+}
+
+BlobURLChannel::~BlobURLChannel() = default;
+
+NS_IMETHODIMP
+BlobURLChannel::SetContentType(const nsACString& aContentType) {
+  // If the blob type is empty, set the content type of the channel to the
+  // empty string.
+  if (aContentType.IsEmpty()) {
+    mContentType.Truncate();
+    return NS_OK;
+  }
+
+  return nsBaseChannel::SetContentType(aContentType);
+}
+
+nsresult BlobURLChannel::OpenContentStream(bool aAsync,
+                                           nsIInputStream** aResult,
+                                           nsIChannel** aChannel) {
+  if (mContentStreamOpened) {
+    return NS_ERROR_ALREADY_OPENED;
+  }
+
+  mContentStreamOpened = true;
+
+  nsCOMPtr<nsIURI> uri;
+  nsresult rv = GetURI(getter_AddRefs(uri));
+  NS_ENSURE_SUCCESS(rv, NS_ERROR_MALFORMED_URI);
+
+  RefPtr<BlobURL> blobURL;
+  rv = uri->QueryInterface(kHOSTOBJECTURICID, getter_AddRefs(blobURL));
+
+  if (NS_WARN_IF(NS_FAILED(rv)) || NS_WARN_IF(!blobURL)) {
+    return NS_ERROR_MALFORMED_URI;
+  }
+
+  if (blobURL->Revoked()) {
+#ifdef MOZ_WIDGET_ANDROID
+    nsCOMPtr<nsILoadInfo> loadInfo;
+    GetLoadInfo(getter_AddRefs(loadInfo));
+    // if the channel was not triggered by the system principal,
+    // then we return here because the URL had been revoked
+    if (loadInfo && !loadInfo->TriggeringPrincipal()->IsSystemPrincipal()) {
+      return NS_ERROR_MALFORMED_URI;
+    }
+#else
+    return NS_ERROR_MALFORMED_URI;
+#endif
+  }
+
+  nsCOMPtr<nsIInputStream> inputStream =
+      BlobURLInputStream::Create(this, blobURL);
+  if (NS_WARN_IF(!inputStream)) {
+    return NS_ERROR_MALFORMED_URI;
+  }
+
+  EnableSynthesizedProgressEvents(true);
+
+  inputStream.forget(aResult);
+
+  return NS_OK;
+}
diff --git a/dom/file/uri/BlobURLChannel.h b/dom/file/uri/BlobURLChannel.h
new file mode 100644
index 0000000000..232537171e
--- /dev/null
+++ b/dom/file/uri/BlobURLChannel.h
@@ -0,0 +1,37 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_BlobURLChannel_h
+#define mozilla_dom_BlobURLChannel_h
+
+#include "nsBaseChannel.h"
+#include "nsCOMPtr.h"
+#include "nsIInputStream.h"
+
+class nsIURI;
+
+namespace mozilla::dom {
+
+class BlobImpl;
+
+class BlobURLChannel final : public nsBaseChannel {
+ public:
+  BlobURLChannel(nsIURI* aURI, nsILoadInfo* aLoadInfo);
+
+  NS_IMETHOD SetContentType(const nsACString& aContentType) override;
+
+ private:
+  ~BlobURLChannel() override;
+
+  nsresult OpenContentStream(bool aAsync, nsIInputStream** aResult,
+                             nsIChannel** aChannel) override;
+
+  bool mContentStreamOpened;
+};
+
+}  // namespace mozilla::dom
+
+#endif /* mozilla_dom_BlobURLChannel_h */
diff --git a/dom/file/uri/BlobURLInputStream.cpp b/dom/file/uri/BlobURLInputStream.cpp
new file mode 100644
index 0000000000..23bcff19e6
--- /dev/null
+++ b/dom/file/uri/BlobURLInputStream.cpp
@@ -0,0 +1,569 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "BlobURLInputStream.h"
+#include "BlobURL.h"
+#include "BlobURLChannel.h"
+#include "BlobURLProtocolHandler.h"
+
+#include "mozilla/ScopeExit.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/dom/IPCBlobUtils.h"
+#include "nsStreamUtils.h"
+#include "nsMimeTypes.h"
+
+namespace mozilla::dom {
+
+NS_IMPL_ADDREF(BlobURLInputStream);
+NS_IMPL_RELEASE(BlobURLInputStream);
+
+NS_INTERFACE_MAP_BEGIN(BlobURLInputStream)
+  NS_INTERFACE_MAP_ENTRY(nsIInputStream)
+  NS_INTERFACE_MAP_ENTRY(nsIAsyncInputStream)
+  NS_INTERFACE_MAP_ENTRY(nsIInputStreamLength)
+  NS_INTERFACE_MAP_ENTRY(nsIAsyncInputStreamLength)
+  NS_INTERFACE_MAP_ENTRY(nsIInputStreamCallback)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIAsyncInputStream)
+NS_INTERFACE_MAP_END
+
+/* static */
+already_AddRefed<nsIInputStream> BlobURLInputStream::Create(
+    BlobURLChannel* const aChannel, BlobURL* const aBlobURL) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (NS_WARN_IF(!aChannel) || NS_WARN_IF(!aBlobURL)) {
+    return nullptr;
+  }
+
+  nsAutoCString spec;
+
+  nsresult rv = aBlobURL->GetSpec(spec);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+
+  return MakeAndAddRef<BlobURLInputStream>(aChannel, spec);
+}
+
+// from nsIInputStream interface
+NS_IMETHODIMP BlobURLInputStream::Close() {
+  return CloseWithStatus(NS_BASE_STREAM_CLOSED);
+}
+
+NS_IMETHODIMP BlobURLInputStream::Available(uint64_t* aLength) {
+  MutexAutoLock lock(mStateMachineMutex);
+
+  if (mState == State::ERROR) {
+    MOZ_ASSERT(NS_FAILED(mError));
+    return mError;
+  }
+
+  if (mState == State::CLOSED) {
+    return NS_BASE_STREAM_CLOSED;
+  }
+
+  if (mState == State::READY) {
+    MOZ_ASSERT(mAsyncInputStream);
+    return mAsyncInputStream->Available(aLength);
+  }
+
+  return NS_BASE_STREAM_WOULD_BLOCK;
+}
+
+NS_IMETHODIMP BlobURLInputStream::Read(char* aBuffer, uint32_t aCount,
+                                       uint32_t* aReadCount) {
+  MutexAutoLock lock(mStateMachineMutex);
+  if (mState == State::ERROR) {
+    MOZ_ASSERT(NS_FAILED(mError));
+    return mError;
+  }
+
+  // Read() should not return NS_BASE_STREAM_CLOSED if stream is closed.
+  // A read count of 0 should indicate closed or consumed stream.
+  // See:
+  // https://searchfox.org/mozilla-central/rev/559b25eb41c1cbffcb90a34e008b8288312fcd25/xpcom/io/nsIInputStream.idl#104
+  if (mState == State::CLOSED) {
+    *aReadCount = 0;
+    return NS_OK;
+  }
+
+  if (mState == State::READY) {
+    MOZ_ASSERT(mAsyncInputStream);
+    nsresult rv = mAsyncInputStream->Read(aBuffer, aCount, aReadCount);
+    if (NS_SUCCEEDED(rv) && aReadCount && !*aReadCount) {
+      mState = State::CLOSED;
+      ReleaseUnderlyingStream(lock);
+    }
+    return rv;
+  }
+
+  return NS_BASE_STREAM_WOULD_BLOCK;
+}
+
+NS_IMETHODIMP BlobURLInputStream::ReadSegments(nsWriteSegmentFun aWriter,
+                                               void* aClosure, uint32_t aCount,
+                                               uint32_t* aResult) {
+  // This means the caller will have to wrap the stream in an
+  // nsBufferedInputStream in order to use ReadSegments
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP BlobURLInputStream::IsNonBlocking(bool* aNonBlocking) {
+  *aNonBlocking = true;
+  return NS_OK;
+}
+
+// from nsIAsyncInputStream interface
+NS_IMETHODIMP BlobURLInputStream::CloseWithStatus(nsresult aStatus) {
+  MutexAutoLock lock(mStateMachineMutex);
+  if (mState == State::READY) {
+    MOZ_ASSERT(mAsyncInputStream);
+    mAsyncInputStream->CloseWithStatus(aStatus);
+  }
+
+  mState = State::CLOSED;
+  ReleaseUnderlyingStream(lock);
+  return NS_OK;
+}
+
+NS_IMETHODIMP BlobURLInputStream::AsyncWait(nsIInputStreamCallback* aCallback,
+                                            uint32_t aFlags,
+                                            uint32_t aRequestedCount,
+                                            nsIEventTarget* aEventTarget) {
+  MutexAutoLock lock(mStateMachineMutex);
+
+  if (mState == State::ERROR) {
+    MOZ_ASSERT(NS_FAILED(mError));
+    return NS_ERROR_FAILURE;
+  }
+
+  // Pre-empting a valid callback with another is not allowed.
+  if (NS_WARN_IF(mAsyncWaitCallback && aCallback &&
+                 mAsyncWaitCallback != aCallback)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  mAsyncWaitTarget = aEventTarget;
+  mAsyncWaitRequestedCount = aRequestedCount;
+  mAsyncWaitFlags = aFlags;
+  mAsyncWaitCallback = aCallback;
+
+  if (mState == State::INITIAL) {
+    mState = State::WAITING;
+    // RetrieveBlobData will execute NotifyWWaitTarget() when retrieve succeeds
+    // or fails
+    if (NS_IsMainThread()) {
+      RetrieveBlobData(lock);
+      return NS_OK;
+    }
+
+    nsCOMPtr<nsIRunnable> runnable = mozilla::NewRunnableMethod(
+        "BlobURLInputStream::CallRetrieveBlobData", this,
+        &BlobURLInputStream::CallRetrieveBlobData);
+    NS_DispatchToMainThread(runnable.forget(), NS_DISPATCH_NORMAL);
+    return NS_OK;
+  }
+
+  if (mState == State::WAITING) {
+    // RetrieveBlobData is already in progress and will execute
+    // NotifyWaitTargets when retrieve succeeds or fails
+    return NS_OK;
+  }
+
+  if (mState == State::READY) {
+    // Ask the blob's input stream if reading is possible or not
+    return mAsyncInputStream->AsyncWait(
+        mAsyncWaitCallback ? this : nullptr, mAsyncWaitFlags,
+        mAsyncWaitRequestedCount, mAsyncWaitTarget);
+  }
+
+  MOZ_ASSERT(mState == State::CLOSED);
+  NotifyWaitTargets(lock);
+  return NS_OK;
+}
+
+// from nsIInputStreamLength interface
+NS_IMETHODIMP BlobURLInputStream::Length(int64_t* aLength) {
+  MutexAutoLock lock(mStateMachineMutex);
+
+  if (mState == State::CLOSED) {
+    return NS_BASE_STREAM_CLOSED;
+  }
+
+  if (mState == State::ERROR) {
+    MOZ_ASSERT(NS_FAILED(mError));
+    return NS_ERROR_FAILURE;
+  }
+
+  if (mState == State::READY) {
+    *aLength = mBlobSize;
+    return NS_OK;
+  }
+  return NS_BASE_STREAM_WOULD_BLOCK;
+}
+
+// from nsIAsyncInputStreamLength interface
+NS_IMETHODIMP BlobURLInputStream::AsyncLengthWait(
+    nsIInputStreamLengthCallback* aCallback, nsIEventTarget* aEventTarget) {
+  MutexAutoLock lock(mStateMachineMutex);
+
+  if (mState == State::ERROR) {
+    MOZ_ASSERT(NS_FAILED(mError));
+    return mError;
+  }
+
+  // Pre-empting a valid callback with another is not allowed.
+  if (mAsyncLengthWaitCallback && aCallback) {
+    return NS_ERROR_FAILURE;
+  }
+
+  mAsyncLengthWaitTarget = aEventTarget;
+  mAsyncLengthWaitCallback = aCallback;
+
+  if (mState == State::INITIAL) {
+    mState = State::WAITING;
+    // RetrieveBlobData will execute NotifyWWaitTarget() when retrieve succeeds
+    // or fails
+    if (NS_IsMainThread()) {
+      RetrieveBlobData(lock);
+      return NS_OK;
+    }
+
+    nsCOMPtr<nsIRunnable> runnable = mozilla::NewRunnableMethod(
+        "BlobURLInputStream::CallRetrieveBlobData", this,
+        &BlobURLInputStream::CallRetrieveBlobData);
+    NS_DispatchToMainThread(runnable.forget(), NS_DISPATCH_NORMAL);
+    return NS_OK;
+  }
+
+  if (mState == State::WAITING) {
+    // RetrieveBlobData is already in progress and will execute
+    // NotifyWaitTargets when retrieve succeeds or fails
+    return NS_OK;
+  }
+
+  // Since here the state must be READY (in which case the size of the blob is
+  // already known) or CLOSED, callback can be called immediately
+  NotifyWaitTargets(lock);
+  return NS_OK;
+}
+
+// from nsIInputStreamCallback interface
+NS_IMETHODIMP BlobURLInputStream::OnInputStreamReady(
+    nsIAsyncInputStream* aStream) {
+  nsCOMPtr<nsIInputStreamCallback> callback;
+
+  {
+    MutexAutoLock lock(mStateMachineMutex);
+    MOZ_ASSERT_IF(mAsyncInputStream, aStream == mAsyncInputStream);
+
+    // aborted in the meantime
+    if (!mAsyncWaitCallback) {
+      return NS_OK;
+    }
+
+    mAsyncWaitCallback.swap(callback);
+    mAsyncWaitTarget = nullptr;
+  }
+
+  MOZ_ASSERT(callback);
+  return callback->OnInputStreamReady(this);
+}
+
+// from nsIInputStreamLengthCallback interface
+NS_IMETHODIMP BlobURLInputStream::OnInputStreamLengthReady(
+    nsIAsyncInputStreamLength* aStream, int64_t aLength) {
+  nsCOMPtr<nsIInputStreamLengthCallback> callback;
+  {
+    MutexAutoLock lock(mStateMachineMutex);
+
+    // aborted in the meantime
+    if (!mAsyncLengthWaitCallback) {
+      return NS_OK;
+    }
+
+    mAsyncLengthWaitCallback.swap(callback);
+    mAsyncLengthWaitCallback = nullptr;
+  }
+
+  return callback->OnInputStreamLengthReady(this, aLength);
+}
+
+// private:
+BlobURLInputStream::~BlobURLInputStream() {
+  if (mChannel) {
+    NS_ReleaseOnMainThread("BlobURLInputStream::mChannel", mChannel.forget());
+  }
+}
+
+BlobURLInputStream::BlobURLInputStream(BlobURLChannel* const aChannel,
+                                       nsACString& aBlobURLSpec)
+    : mChannel(aChannel),
+      mBlobURLSpec(std::move(aBlobURLSpec)),
+      mStateMachineMutex("BlobURLInputStream::mStateMachineMutex"),
+      mState(State::INITIAL),
+      mError(NS_OK),
+      mBlobSize(-1),
+      mAsyncWaitFlags(),
+      mAsyncWaitRequestedCount() {}
+
+void BlobURLInputStream::WaitOnUnderlyingStream(
+    const MutexAutoLock& aProofOfLock) {
+  if (mAsyncWaitCallback || mAsyncWaitTarget) {
+    // AsyncWait should be called on the underlying stream
+    mAsyncInputStream->AsyncWait(mAsyncWaitCallback ? this : nullptr,
+                                 mAsyncWaitFlags, mAsyncWaitRequestedCount,
+                                 mAsyncWaitTarget);
+  }
+
+  if (mAsyncLengthWaitCallback || mAsyncLengthWaitTarget) {
+    // AsyncLengthWait should be called on the underlying stream
+    nsCOMPtr<nsIAsyncInputStreamLength> asyncStreamLength =
+        do_QueryInterface(mAsyncInputStream);
+    if (asyncStreamLength) {
+      asyncStreamLength->AsyncLengthWait(
+          mAsyncLengthWaitCallback ? this : nullptr, mAsyncLengthWaitTarget);
+    }
+  }
+}
+
+void BlobURLInputStream::CallRetrieveBlobData() {
+  MutexAutoLock lock(mStateMachineMutex);
+  RetrieveBlobData(lock);
+}
+
+void BlobURLInputStream::RetrieveBlobData(const MutexAutoLock& aProofOfLock) {
+  MOZ_ASSERT(NS_IsMainThread(), "Only call on main thread");
+
+  MOZ_ASSERT(mState == State::WAITING);
+
+  auto cleanupOnEarlyExit = MakeScopeExit([&] {
+    mState = State::ERROR;
+    mError = NS_ERROR_FAILURE;
+    NS_ReleaseOnMainThread("BlobURLInputStream::mChannel", mChannel.forget());
+    NotifyWaitTargets(aProofOfLock);
+  });
+
+  nsCOMPtr<nsILoadInfo> loadInfo = mChannel->LoadInfo();
+  nsCOMPtr<nsIPrincipal> triggeringPrincipal;
+  nsCOMPtr<nsIPrincipal> loadingPrincipal;
+  if (NS_WARN_IF(NS_FAILED(loadInfo->GetTriggeringPrincipal(
+          getter_AddRefs(triggeringPrincipal)))) ||
+      NS_WARN_IF(!triggeringPrincipal)) {
+    NS_WARNING("Failed to get owning channel's triggering principal");
+    return;
+  }
+
+  if (NS_WARN_IF(NS_FAILED(
+          loadInfo->GetLoadingPrincipal(getter_AddRefs(loadingPrincipal))))) {
+    NS_WARNING("Failed to get owning channel's loading principal");
+    return;
+  }
+
+  Maybe<nsID> agentClusterId;
+  Maybe<ClientInfo> clientInfo = loadInfo->GetClientInfo();
+  if (clientInfo.isSome()) {
+    agentClusterId = clientInfo->AgentClusterId();
+  }
+
+  if (XRE_IsParentProcess() || !BlobURLSchemeIsHTTPOrHTTPS(mBlobURLSpec)) {
+    RefPtr<BlobImpl> blobImpl;
+
+    // Since revoked blobs are also retrieved, it is possible that the blob no
+    // longer exists (due to the 5 second timeout) when execution reaches here
+    if (!BlobURLProtocolHandler::GetDataEntry(
+            mBlobURLSpec, getter_AddRefs(blobImpl), loadingPrincipal,
+            triggeringPrincipal, loadInfo->GetOriginAttributes(),
+            loadInfo->GetInnerWindowID(), agentClusterId,
+            true /* AlsoIfRevoked */)) {
+      NS_WARNING("Failed to get data entry principal. URL revoked?");
+      return;
+    }
+
+    if (NS_WARN_IF(
+            NS_FAILED(StoreBlobImplStream(blobImpl.forget(), aProofOfLock)))) {
+      return;
+    }
+
+    mState = State::READY;
+
+    // By design, execution can only reach here when a caller has called
+    // AsyncWait or AsyncLengthWait on this stream. The underlying stream is
+    // valid, but the caller should not be informed until that stream has data
+    // to read or it is closed.
+    WaitOnUnderlyingStream(aProofOfLock);
+
+    cleanupOnEarlyExit.release();
+    return;
+  }
+
+  ContentChild* contentChild{ContentChild::GetSingleton()};
+  MOZ_ASSERT(contentChild);
+
+  const RefPtr<BlobURLInputStream> self = this;
+
+  cleanupOnEarlyExit.release();
+
+  contentChild
+      ->SendBlobURLDataRequest(mBlobURLSpec, triggeringPrincipal,
+                               loadingPrincipal,
+                               loadInfo->GetOriginAttributes(),
+                               loadInfo->GetInnerWindowID(), agentClusterId)
+      ->Then(
+          GetCurrentSerialEventTarget(), __func__,
+          [self](const BlobURLDataRequestResult& aResult) {
+            MutexAutoLock lock(self->mStateMachineMutex);
+            if (aResult.type() == BlobURLDataRequestResult::TIPCBlob) {
+              if (self->mState == State::WAITING) {
+                RefPtr<BlobImpl> blobImpl =
+                    IPCBlobUtils::Deserialize(aResult.get_IPCBlob());
+                if (blobImpl && self->StoreBlobImplStream(blobImpl.forget(),
+                                                          lock) == NS_OK) {
+                  self->mState = State::READY;
+                  // By design, execution can only reach here when a caller has
+                  // called AsyncWait or AsyncLengthWait on this stream. The
+                  // underlying stream is valid, but the caller should not be
+                  // informed until that stream has data to read or it is
+                  // closed.
+                  self->WaitOnUnderlyingStream(lock);
+                  return;
+                }
+              } else {
+                MOZ_ASSERT(self->mState == State::CLOSED);
+                // Callback can be called immediately
+                self->NotifyWaitTargets(lock);
+                return;
+              }
+            }
+            NS_WARNING("Blob data was not retrieved!");
+            self->mState = State::ERROR;
+            self->mError = aResult.type() == BlobURLDataRequestResult::Tnsresult
+                               ? aResult.get_nsresult()
+                               : NS_ERROR_FAILURE;
+            NS_ReleaseOnMainThread("BlobURLInputStream::mChannel",
+                                   self->mChannel.forget());
+            self->NotifyWaitTargets(lock);
+          },
+          [self](mozilla::ipc::ResponseRejectReason aReason) {
+            MutexAutoLock lock(self->mStateMachineMutex);
+            NS_WARNING("IPC call to SendBlobURLDataRequest failed!");
+            self->mState = State::ERROR;
+            self->mError = NS_ERROR_FAILURE;
+            NS_ReleaseOnMainThread("BlobURLInputStream::mChannel",
+                                   self->mChannel.forget());
+            self->NotifyWaitTargets(lock);
+          });
+}
+
+nsresult BlobURLInputStream::StoreBlobImplStream(
+    already_AddRefed<BlobImpl> aBlobImpl, const MutexAutoLock& aProofOfLock) {
+  MOZ_ASSERT(NS_IsMainThread(), "Only call on main thread");
+  const RefPtr<BlobImpl> blobImpl = aBlobImpl;
+  nsAutoString blobContentType;
+  nsAutoCString channelContentType;
+
+  blobImpl->GetType(blobContentType);
+  mChannel->GetContentType(channelContentType);
+  // A empty content type is the correct channel content type in the case of a
+  // fetch of a blob where the type was not set. It is invalid in others cases
+  // such as a XHR (See https://xhr.spec.whatwg.org/#response-mime-type). The
+  // XMLHttpRequestMainThread will set the channel content type to the correct
+  // fallback value before this point, so we need to be careful to only override
+  // it when the blob type is valid.
+  if (!blobContentType.IsEmpty() ||
+      channelContentType.EqualsLiteral(UNKNOWN_CONTENT_TYPE)) {
+    mChannel->SetContentType(NS_ConvertUTF16toUTF8(blobContentType));
+  }
+
+  auto cleanupOnExit = MakeScopeExit([&] { mChannel = nullptr; });
+
+  if (blobImpl->IsFile()) {
+    nsAutoString filename;
+    blobImpl->GetName(filename);
+
+    // Don't overwrite existing name.
+    nsString ignored;
+    bool hasName =
+        NS_SUCCEEDED(mChannel->GetContentDispositionFilename(ignored));
+
+    if (!filename.IsEmpty() && !hasName) {
+      mChannel->SetContentDispositionFilename(filename);
+    }
+  }
+
+  mozilla::ErrorResult errorResult;
+
+  mBlobSize = blobImpl->GetSize(errorResult);
+
+  if (NS_WARN_IF(errorResult.Failed())) {
+    return errorResult.StealNSResult();
+  }
+
+  mChannel->SetContentLength(mBlobSize);
+
+  nsCOMPtr<nsIInputStream> inputStream;
+  blobImpl->CreateInputStream(getter_AddRefs(inputStream), errorResult);
+
+  if (NS_WARN_IF(errorResult.Failed())) {
+    return errorResult.StealNSResult();
+  }
+
+  if (NS_WARN_IF(!inputStream)) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  nsresult rv = NS_MakeAsyncNonBlockingInputStream(
+      inputStream.forget(), getter_AddRefs(mAsyncInputStream));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  if (NS_WARN_IF(!mAsyncInputStream)) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  return NS_OK;
+}
+
+void BlobURLInputStream::NotifyWaitTargets(const MutexAutoLock& aProofOfLock) {
+  if (mAsyncWaitCallback) {
+    auto callback = mAsyncWaitTarget
+                        ? NS_NewInputStreamReadyEvent(
+                              "BlobURLInputStream::OnInputStreamReady",
+                              mAsyncWaitCallback, mAsyncWaitTarget)
+                        : mAsyncWaitCallback;
+
+    mAsyncWaitCallback = nullptr;
+    mAsyncWaitTarget = nullptr;
+    callback->OnInputStreamReady(this);
+  }
+
+  if (mAsyncLengthWaitCallback) {
+    const RefPtr<BlobURLInputStream> self = this;
+    nsCOMPtr<nsIRunnable> runnable = NS_NewRunnableFunction(
+        "BlobURLInputStream::OnInputStreamLengthReady", [self] {
+          self->mAsyncLengthWaitCallback->OnInputStreamLengthReady(
+              self, self->mBlobSize);
+        });
+
+    mAsyncLengthWaitCallback = nullptr;
+
+    if (mAsyncLengthWaitTarget) {
+      mAsyncLengthWaitTarget->Dispatch(runnable, NS_DISPATCH_NORMAL);
+      mAsyncLengthWaitTarget = nullptr;
+    } else {
+      runnable->Run();
+    }
+  }
+}
+
+void BlobURLInputStream::ReleaseUnderlyingStream(
+    const MutexAutoLock& aProofOfLock) {
+  mAsyncInputStream = nullptr;
+  mBlobSize = -1;
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/uri/BlobURLInputStream.h b/dom/file/uri/BlobURLInputStream.h
new file mode 100644
index 0000000000..b9215e5ffd
--- /dev/null
+++ b/dom/file/uri/BlobURLInputStream.h
@@ -0,0 +1,81 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_BlobURLInputStream_h
+#define mozilla_dom_BlobURLInputStream_h
+
+#include "mozilla/dom/BlobImpl.h"
+#include "mozilla/Mutex.h"
+#include "nsCOMPtr.h"
+#include "nsIAsyncInputStream.h"
+#include "nsIInputStreamLength.h"
+
+namespace mozilla::dom {
+
+class BlobURL;
+class BlobURLChannel;
+class BlobURLInputStream final : public nsIAsyncInputStream,
+                                 public nsIInputStreamLength,
+                                 public nsIAsyncInputStreamLength,
+                                 public nsIInputStreamCallback,
+                                 public nsIInputStreamLengthCallback {
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIINPUTSTREAM
+  NS_DECL_NSIASYNCINPUTSTREAM
+  NS_DECL_NSIINPUTSTREAMLENGTH
+  NS_DECL_NSIASYNCINPUTSTREAMLENGTH
+  NS_DECL_NSIINPUTSTREAMCALLBACK
+  NS_DECL_NSIINPUTSTREAMLENGTHCALLBACK
+
+  static already_AddRefed<nsIInputStream> Create(BlobURLChannel* const aChannel,
+                                                 BlobURL* const aBlobURL);
+
+  BlobURLInputStream(BlobURLChannel* const aChannel, nsACString& aBlobURLSpec);
+
+ private:
+  enum class State { INITIAL, READY, WAITING, CLOSED, ERROR };
+
+  ~BlobURLInputStream();
+
+  void WaitOnUnderlyingStream(const MutexAutoLock& aProofOfLock);
+
+  // This method should only be used to call RetrieveBlobData in a different
+  // thread
+  void CallRetrieveBlobData();
+
+  void RetrieveBlobData(const MutexAutoLock& aProofOfLock);
+
+  nsresult StoreBlobImplStream(already_AddRefed<BlobImpl> aBlobImpl,
+                               const MutexAutoLock& aProofOfLock);
+  void NotifyWaitTargets(const MutexAutoLock& aProofOfLock);
+  void ReleaseUnderlyingStream(const MutexAutoLock& aProofOfLock);
+
+  RefPtr<BlobURLChannel> mChannel;
+  const nsCString mBlobURLSpec;
+
+  // Non-recursive mutex introduced in order to guard access to mState, mError
+  // and mAsyncInputStream
+  Mutex mStateMachineMutex MOZ_UNANNOTATED;
+  State mState;
+  // Stores the error code if stream is in error state
+  nsresult mError;
+
+  int64_t mBlobSize;
+
+  nsCOMPtr<nsIAsyncInputStream> mAsyncInputStream;
+  nsCOMPtr<nsIInputStreamCallback> mAsyncWaitCallback;
+  nsCOMPtr<nsIEventTarget> mAsyncWaitTarget;
+  uint32_t mAsyncWaitFlags;
+  uint32_t mAsyncWaitRequestedCount;
+
+  nsCOMPtr<nsIInputStreamLengthCallback> mAsyncLengthWaitCallback;
+  nsCOMPtr<nsIEventTarget> mAsyncLengthWaitTarget;
+};
+
+}  // namespace mozilla::dom
+
+#endif /* mozilla_dom_BlobURLInputStream_h */
diff --git a/dom/file/uri/BlobURLProtocolHandler.cpp b/dom/file/uri/BlobURLProtocolHandler.cpp
new file mode 100644
index 0000000000..cb5cca3f5f
--- /dev/null
+++ b/dom/file/uri/BlobURLProtocolHandler.cpp
@@ -0,0 +1,990 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "BlobURLProtocolHandler.h"
+#include "BlobURLChannel.h"
+#include "mozilla/dom/BlobURL.h"
+
+#include "mozilla/dom/ChromeUtils.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/Exceptions.h"
+#include "mozilla/dom/BlobImpl.h"
+#include "mozilla/dom/IPCBlobUtils.h"
+#include "mozilla/dom/MediaSource.h"
+#include "mozilla/ipc/IPCStreamUtils.h"
+#include "mozilla/AppShutdown.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/LoadInfo.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/NullPrincipal.h"
+#include "mozilla/OriginAttributes.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/SchedulerGroup.h"
+#include "mozilla/ScopeExit.h"
+#include "nsClassHashtable.h"
+#include "nsContentUtils.h"
+#include "nsError.h"
+#include "nsIAsyncShutdown.h"
+#include "nsIDUtils.h"
+#include "nsIException.h"  // for nsIStackFrame
+#include "nsIMemoryReporter.h"
+#include "nsIPrincipal.h"
+#include "nsIUUIDGenerator.h"
+#include "nsNetUtil.h"
+#include "nsReadableUtils.h"
+
+#define RELEASING_TIMER 5000
+
+namespace mozilla {
+
+using namespace ipc;
+
+namespace dom {
+
+// -----------------------------------------------------------------------
+// Hash table
+struct DataInfo {
+  enum ObjectType { eBlobImpl, eMediaSource };
+
+  DataInfo(mozilla::dom::BlobImpl* aBlobImpl, nsIPrincipal* aPrincipal,
+           const Maybe<nsID>& aAgentClusterId)
+      : mObjectType(eBlobImpl),
+        mBlobImpl(aBlobImpl),
+        mPrincipal(aPrincipal),
+        mAgentClusterId(aAgentClusterId),
+        mRevoked(false) {
+    MOZ_ASSERT(aPrincipal);
+  }
+
+  DataInfo(MediaSource* aMediaSource, nsIPrincipal* aPrincipal,
+           const Maybe<nsID>& aAgentClusterId)
+      : mObjectType(eMediaSource),
+        mMediaSource(aMediaSource),
+        mPrincipal(aPrincipal),
+        mAgentClusterId(aAgentClusterId),
+        mRevoked(false) {
+    MOZ_ASSERT(aPrincipal);
+  }
+
+  ObjectType mObjectType;
+
+  RefPtr<BlobImpl> mBlobImpl;
+  RefPtr<MediaSource> mMediaSource;
+
+  nsCOMPtr<nsIPrincipal> mPrincipal;
+  Maybe<nsID> mAgentClusterId;
+
+  nsCString mStack;
+
+  // When a blobURL is revoked, we keep it alive for RELEASING_TIMER
+  // milliseconds in order to support pending operations such as navigation,
+  // download and so on.
+  bool mRevoked;
+};
+
+// The mutex is locked whenever gDataTable is changed, or if gDataTable
+// is accessed off-main-thread.
+static StaticMutex sMutex MOZ_UNANNOTATED;
+
+// All changes to gDataTable must happen on the main thread, while locking
+// sMutex. Reading from gDataTable on the main thread may happen without
+// locking, since no changes are possible. Reading it from another thread
+// must also lock sMutex to prevent data races.
+static nsClassHashtable<nsCStringHashKey, mozilla::dom::DataInfo>* gDataTable;
+
+static mozilla::dom::DataInfo* GetDataInfo(const nsACString& aUri,
+                                           bool aAlsoIfRevoked = false) {
+  if (!gDataTable) {
+    return nullptr;
+  }
+
+  // Let's remove any fragment from this URI.
+  int32_t fragmentPos = aUri.FindChar('#');
+
+  mozilla::dom::DataInfo* res;
+  if (fragmentPos < 0) {
+    res = gDataTable->Get(aUri);
+  } else {
+    res = gDataTable->Get(StringHead(aUri, fragmentPos));
+  }
+
+  if (!aAlsoIfRevoked && res && res->mRevoked) {
+    return nullptr;
+  }
+
+  return res;
+}
+
+static mozilla::dom::DataInfo* GetDataInfoFromURI(nsIURI* aURI,
+                                                  bool aAlsoIfRevoked = false) {
+  if (!aURI) {
+    return nullptr;
+  }
+
+  nsCString spec;
+  nsresult rv = aURI->GetSpec(spec);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+
+  return GetDataInfo(spec, aAlsoIfRevoked);
+}
+
+// Memory reporting for the hash table.
+void BroadcastBlobURLRegistration(const nsACString& aURI,
+                                  mozilla::dom::BlobImpl* aBlobImpl,
+                                  nsIPrincipal* aPrincipal,
+                                  const Maybe<nsID>& aAgentClusterId) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(aBlobImpl);
+  MOZ_ASSERT(aPrincipal);
+
+  if (XRE_IsParentProcess()) {
+    dom::ContentParent::BroadcastBlobURLRegistration(
+        aURI, aBlobImpl, aPrincipal, aAgentClusterId);
+    return;
+  }
+
+  IPCBlob ipcBlob;
+  nsresult rv = IPCBlobUtils::Serialize(aBlobImpl, ipcBlob);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return;
+  }
+
+  dom::ContentChild* cc = dom::ContentChild::GetSingleton();
+  Unused << NS_WARN_IF(!cc->SendStoreAndBroadcastBlobURLRegistration(
+      nsCString(aURI), ipcBlob, aPrincipal, aAgentClusterId));
+}
+
+void BroadcastBlobURLUnregistration(const nsCString& aURI,
+                                    nsIPrincipal* aPrincipal) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (XRE_IsParentProcess()) {
+    dom::ContentParent::BroadcastBlobURLUnregistration(aURI, aPrincipal);
+    return;
+  }
+
+  dom::ContentChild* cc = dom::ContentChild::GetSingleton();
+  if (cc) {
+    Unused << NS_WARN_IF(
+        !cc->SendUnstoreAndBroadcastBlobURLUnregistration(aURI, aPrincipal));
+  }
+}
+
+class BlobURLsReporter final : public nsIMemoryReporter {
+ public:
+  NS_DECL_ISUPPORTS
+
+  NS_IMETHOD CollectReports(nsIHandleReportCallback* aCallback,
+                            nsISupports* aData, bool aAnonymize) override {
+    MOZ_ASSERT(NS_IsMainThread(),
+               "without locking gDataTable is main-thread only");
+    if (!gDataTable) {
+      return NS_OK;
+    }
+
+    nsTHashMap<nsPtrHashKey<mozilla::dom::BlobImpl>, uint32_t> refCounts;
+
+    // Determine number of URLs per mozilla::dom::BlobImpl, to handle the case
+    // where it's > 1.
+    for (const auto& entry : *gDataTable) {
+      if (entry.GetWeak()->mObjectType != mozilla::dom::DataInfo::eBlobImpl) {
+        continue;
+      }
+
+      mozilla::dom::BlobImpl* blobImpl = entry.GetWeak()->mBlobImpl;
+      MOZ_ASSERT(blobImpl);
+
+      refCounts.LookupOrInsert(blobImpl, 0) += 1;
+    }
+
+    for (const auto& entry : *gDataTable) {
+      nsCStringHashKey::KeyType key = entry.GetKey();
+      mozilla::dom::DataInfo* info = entry.GetWeak();
+
+      if (entry.GetWeak()->mObjectType == mozilla::dom::DataInfo::eBlobImpl) {
+        mozilla::dom::BlobImpl* blobImpl = entry.GetWeak()->mBlobImpl;
+        MOZ_ASSERT(blobImpl);
+
+        constexpr auto desc =
+            "A blob URL allocated with URL.createObjectURL; the referenced "
+            "blob cannot be freed until all URLs for it have been explicitly "
+            "invalidated with URL.revokeObjectURL."_ns;
+        nsAutoCString path, url, owner, specialDesc;
+        uint64_t size = 0;
+        uint32_t refCount = 1;
+        DebugOnly<bool> blobImplWasCounted;
+
+        blobImplWasCounted = refCounts.Get(blobImpl, &refCount);
+        MOZ_ASSERT(blobImplWasCounted);
+        MOZ_ASSERT(refCount > 0);
+
+        bool isMemoryFile = blobImpl->IsMemoryFile();
+
+        if (isMemoryFile) {
+          ErrorResult rv;
+          size = blobImpl->GetSize(rv);
+          if (NS_WARN_IF(rv.Failed())) {
+            rv.SuppressException();
+            size = 0;
+          }
+        }
+
+        path = isMemoryFile ? "memory-blob-urls/" : "file-blob-urls/";
+        BuildPath(path, key, info, aAnonymize);
+
+        if (refCount > 1) {
+          nsAutoCString addrStr;
+
+          addrStr = "0x";
+          addrStr.AppendInt((uint64_t)(mozilla::dom::BlobImpl*)blobImpl, 16);
+
+          path += " ";
+          path.AppendInt(refCount);
+          path += "@";
+          path += addrStr;
+
+          specialDesc = desc;
+          specialDesc += "\n\nNOTE: This blob (address ";
+          specialDesc += addrStr;
+          specialDesc += ") has ";
+          specialDesc.AppendInt(refCount);
+          specialDesc += " URLs.";
+          if (isMemoryFile) {
+            specialDesc += " Its size is divided ";
+            specialDesc += refCount > 2 ? "among" : "between";
+            specialDesc += " them in this report.";
+          }
+        }
+
+        const nsACString& descString =
+            specialDesc.IsEmpty() ? static_cast<const nsACString&>(desc)
+                                  : static_cast<const nsACString&>(specialDesc);
+        if (isMemoryFile) {
+          aCallback->Callback(""_ns, path, KIND_OTHER, UNITS_BYTES,
+                              size / refCount, descString, aData);
+        } else {
+          aCallback->Callback(""_ns, path, KIND_OTHER, UNITS_COUNT, 1,
+                              descString, aData);
+        }
+        continue;
+      }
+
+      // Just report the path for the MediaSource.
+      nsAutoCString path;
+      path = "media-source-urls/";
+      BuildPath(path, key, info, aAnonymize);
+
+      constexpr auto desc =
+          "An object URL allocated with URL.createObjectURL; the referenced "
+          "data cannot be freed until all URLs for it have been explicitly "
+          "invalidated with URL.revokeObjectURL."_ns;
+
+      aCallback->Callback(""_ns, path, KIND_OTHER, UNITS_COUNT, 1, desc, aData);
+    }
+
+    return NS_OK;
+  }
+
+  // Initialize info->mStack to record JS stack info, if enabled.
+  // The string generated here is used in ReportCallback, below.
+  static void GetJSStackForBlob(mozilla::dom::DataInfo* aInfo) {
+    nsCString& stack = aInfo->mStack;
+    MOZ_ASSERT(stack.IsEmpty());
+    const uint32_t maxFrames =
+        Preferences::GetUint("memory.blob_report.stack_frames");
+
+    if (maxFrames == 0) {
+      return;
+    }
+
+    nsCOMPtr<nsIStackFrame> frame = dom::GetCurrentJSStack(maxFrames);
+
+    nsAutoCString origin;
+
+    aInfo->mPrincipal->GetPrePath(origin);
+
+    // If we got a frame, we better have a current JSContext.  This is cheating
+    // a bit; ideally we'd have our caller pass in a JSContext, or have
+    // GetCurrentJSStack() hand out the JSContext it found.
+    JSContext* cx = frame ? nsContentUtils::GetCurrentJSContext() : nullptr;
+
+    while (frame) {
+      nsString fileNameUTF16;
+      frame->GetFilename(cx, fileNameUTF16);
+
+      int32_t lineNumber = frame->GetLineNumber(cx);
+
+      if (!fileNameUTF16.IsEmpty()) {
+        NS_ConvertUTF16toUTF8 fileName(fileNameUTF16);
+        stack += "js(";
+        if (!origin.IsEmpty()) {
+          // Make the file name root-relative for conciseness if possible.
+          const char* originData;
+          uint32_t originLen;
+
+          originLen = origin.GetData(&originData);
+          // If fileName starts with origin + "/", cut up to that "/".
+          if (fileName.Length() >= originLen + 1 &&
+              memcmp(fileName.get(), originData, originLen) == 0 &&
+              fileName[originLen] == '/') {
+            fileName.Cut(0, originLen);
+          }
+        }
+        fileName.ReplaceChar('/', '\\');
+        stack += fileName;
+        if (lineNumber > 0) {
+          stack += ", line=";
+          stack.AppendInt(lineNumber);
+        }
+        stack += ")/";
+      }
+
+      frame = frame->GetCaller(cx);
+    }
+  }
+
+ private:
+  ~BlobURLsReporter() = default;
+
+  static void BuildPath(nsAutoCString& path, nsCStringHashKey::KeyType aKey,
+                        mozilla::dom::DataInfo* aInfo, bool anonymize) {
+    nsAutoCString url, owner;
+    aInfo->mPrincipal->GetAsciiSpec(owner);
+    if (!owner.IsEmpty()) {
+      owner.ReplaceChar('/', '\\');
+      path += "owner(";
+      if (anonymize) {
+        path += "<anonymized>";
+      } else {
+        path += owner;
+      }
+      path += ")";
+    } else {
+      path += "owner unknown";
+    }
+    path += "/";
+    if (anonymize) {
+      path += "<anonymized-stack>";
+    } else {
+      path += aInfo->mStack;
+    }
+    url = aKey;
+    url.ReplaceChar('/', '\\');
+    if (anonymize) {
+      path += "<anonymized-url>";
+    } else {
+      path += url;
+    }
+  }
+};
+
+NS_IMPL_ISUPPORTS(BlobURLsReporter, nsIMemoryReporter)
+
+class ReleasingTimerHolder final : public Runnable,
+                                   public nsITimerCallback,
+                                   public nsIAsyncShutdownBlocker {
+ public:
+  NS_DECL_ISUPPORTS_INHERITED
+
+  static void Create(const nsACString& aURI) {
+    MOZ_ASSERT(NS_IsMainThread());
+
+    RefPtr<ReleasingTimerHolder> holder = new ReleasingTimerHolder(aURI);
+
+    // BlobURLProtocolHandler::RemoveDataEntry potentially happens late. We are
+    // prepared to RevokeUri synchronously if we run after XPCOMWillShutdown,
+    // but we need at least to be able to dispatch to the main thread here.
+    auto raii = MakeScopeExit([holder] { holder->CancelTimerAndRevokeURI(); });
+
+    nsresult rv =
+        SchedulerGroup::Dispatch(TaskCategory::Other, holder.forget());
+    NS_ENSURE_SUCCESS_VOID(rv);
+
+    raii.release();
+  }
+
+  // Runnable interface
+
+  NS_IMETHOD
+  Run() override {
+    RefPtr<ReleasingTimerHolder> self = this;
+    auto raii = MakeScopeExit([self] { self->CancelTimerAndRevokeURI(); });
+
+    nsresult rv = NS_NewTimerWithCallback(
+        getter_AddRefs(mTimer), this, RELEASING_TIMER, nsITimer::TYPE_ONE_SHOT);
+    NS_ENSURE_SUCCESS(rv, NS_OK);
+
+    nsCOMPtr<nsIAsyncShutdownClient> phase = GetShutdownPhase();
+    NS_ENSURE_TRUE(!!phase, NS_OK);
+
+    rv = phase->AddBlocker(this, NS_LITERAL_STRING_FROM_CSTRING(__FILE__),
+                           __LINE__, u"ReleasingTimerHolder shutdown"_ns);
+    NS_ENSURE_SUCCESS(rv, NS_OK);
+
+    raii.release();
+    return NS_OK;
+  }
+
+  // nsITimerCallback interface
+
+  NS_IMETHOD
+  Notify(nsITimer* aTimer) override {
+    RevokeURI();
+    return NS_OK;
+  }
+
+#ifdef MOZ_COLLECTING_RUNNABLE_TELEMETRY
+  using nsINamed::GetName;
+#endif
+
+  // nsIAsyncShutdownBlocker interface
+
+  NS_IMETHOD
+  GetName(nsAString& aName) override {
+    aName.AssignLiteral("ReleasingTimerHolder for blobURL: ");
+    aName.Append(NS_ConvertUTF8toUTF16(mURI));
+    return NS_OK;
+  }
+
+  NS_IMETHOD
+  BlockShutdown(nsIAsyncShutdownClient* aClient) override {
+    CancelTimerAndRevokeURI();
+    return NS_OK;
+  }
+
+  NS_IMETHOD
+  GetState(nsIPropertyBag**) override { return NS_OK; }
+
+ private:
+  explicit ReleasingTimerHolder(const nsACString& aURI)
+      : Runnable("ReleasingTimerHolder"), mURI(aURI) {}
+
+  ~ReleasingTimerHolder() override = default;
+
+  void RevokeURI() {
+    // Remove the shutting down blocker
+    nsCOMPtr<nsIAsyncShutdownClient> phase = GetShutdownPhase();
+    if (phase) {
+      phase->RemoveBlocker(this);
+    }
+
+    MOZ_ASSERT(NS_IsMainThread(),
+               "without locking gDataTable is main-thread only");
+    mozilla::dom::DataInfo* info =
+        GetDataInfo(mURI, true /* We care about revoked dataInfo */);
+    if (!info) {
+      // Already gone!
+      return;
+    }
+
+    MOZ_ASSERT(info->mRevoked);
+
+    StaticMutexAutoLock lock(sMutex);
+    gDataTable->Remove(mURI);
+    if (gDataTable->Count() == 0) {
+      delete gDataTable;
+      gDataTable = nullptr;
+    }
+  }
+
+  void CancelTimerAndRevokeURI() {
+    if (mTimer) {
+      mTimer->Cancel();
+      mTimer = nullptr;
+    }
+
+    RevokeURI();
+  }
+
+  static nsCOMPtr<nsIAsyncShutdownClient> GetShutdownPhase() {
+    nsCOMPtr<nsIAsyncShutdownService> svc = services::GetAsyncShutdownService();
+    NS_ENSURE_TRUE(!!svc, nullptr);
+
+    nsCOMPtr<nsIAsyncShutdownClient> phase;
+    nsresult rv = svc->GetXpcomWillShutdown(getter_AddRefs(phase));
+    NS_ENSURE_SUCCESS(rv, nullptr);
+
+    return phase;
+  }
+
+  nsCString mURI;
+  nsCOMPtr<nsITimer> mTimer;
+};
+
+NS_IMPL_ISUPPORTS_INHERITED(ReleasingTimerHolder, Runnable, nsITimerCallback,
+                            nsIAsyncShutdownBlocker)
+
+template <typename T>
+static void AddDataEntryInternal(const nsACString& aURI, T aObject,
+                                 nsIPrincipal* aPrincipal,
+                                 const Maybe<nsID>& aAgentClusterId) {
+  MOZ_ASSERT(NS_IsMainThread(), "changing gDataTable is main-thread only");
+  StaticMutexAutoLock lock(sMutex);
+  if (!gDataTable) {
+    gDataTable = new nsClassHashtable<nsCStringHashKey, mozilla::dom::DataInfo>;
+  }
+
+  mozilla::UniquePtr<mozilla::dom::DataInfo> info =
+      mozilla::MakeUnique<mozilla::dom::DataInfo>(aObject, aPrincipal,
+                                                  aAgentClusterId);
+  BlobURLsReporter::GetJSStackForBlob(info.get());
+
+  gDataTable->InsertOrUpdate(aURI, std::move(info));
+}
+
+void BlobURLProtocolHandler::Init(void) {
+  static bool initialized = false;
+
+  if (!initialized) {
+    initialized = true;
+    RegisterStrongMemoryReporter(new BlobURLsReporter());
+  }
+}
+
+BlobURLProtocolHandler::BlobURLProtocolHandler() { Init(); }
+
+BlobURLProtocolHandler::~BlobURLProtocolHandler() = default;
+
+/* static */
+nsresult BlobURLProtocolHandler::AddDataEntry(
+    mozilla::dom::BlobImpl* aBlobImpl, nsIPrincipal* aPrincipal,
+    const Maybe<nsID>& aAgentClusterId, nsACString& aUri) {
+  MOZ_ASSERT(aBlobImpl);
+  MOZ_ASSERT(aPrincipal);
+
+  Init();
+
+  nsresult rv = GenerateURIString(aPrincipal, aUri);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  AddDataEntryInternal(aUri, aBlobImpl, aPrincipal, aAgentClusterId);
+
+  BroadcastBlobURLRegistration(aUri, aBlobImpl, aPrincipal, aAgentClusterId);
+  return NS_OK;
+}
+
+/* static */
+nsresult BlobURLProtocolHandler::AddDataEntry(
+    MediaSource* aMediaSource, nsIPrincipal* aPrincipal,
+    const Maybe<nsID>& aAgentClusterId, nsACString& aUri) {
+  MOZ_ASSERT(aMediaSource);
+  MOZ_ASSERT(aPrincipal);
+
+  Init();
+
+  nsresult rv = GenerateURIString(aPrincipal, aUri);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  AddDataEntryInternal(aUri, aMediaSource, aPrincipal, aAgentClusterId);
+  return NS_OK;
+}
+
+/* static */
+void BlobURLProtocolHandler::AddDataEntry(const nsACString& aURI,
+                                          nsIPrincipal* aPrincipal,
+                                          const Maybe<nsID>& aAgentClusterId,
+                                          mozilla::dom::BlobImpl* aBlobImpl) {
+  MOZ_ASSERT(aPrincipal);
+  MOZ_ASSERT(aBlobImpl);
+  AddDataEntryInternal(aURI, aBlobImpl, aPrincipal, aAgentClusterId);
+}
+
+/* static */
+bool BlobURLProtocolHandler::ForEachBlobURL(
+    std::function<bool(mozilla::dom::BlobImpl*, nsIPrincipal*,
+                       const Maybe<nsID>&, const nsACString&, bool aRevoked)>&&
+        aCb) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!gDataTable) {
+    return false;
+  }
+
+  for (const auto& entry : *gDataTable) {
+    mozilla::dom::DataInfo* info = entry.GetWeak();
+    MOZ_ASSERT(info);
+
+    if (info->mObjectType != mozilla::dom::DataInfo::eBlobImpl) {
+      continue;
+    }
+
+    MOZ_ASSERT(info->mBlobImpl);
+    if (!aCb(info->mBlobImpl, info->mPrincipal, info->mAgentClusterId,
+             entry.GetKey(), info->mRevoked)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+/*static */
+void BlobURLProtocolHandler::RemoveDataEntry(const nsACString& aUri,
+                                             bool aBroadcastToOtherProcesses) {
+  MOZ_ASSERT(NS_IsMainThread(), "changing gDataTable is main-thread only");
+  if (!gDataTable) {
+    return;
+  }
+  mozilla::dom::DataInfo* info = GetDataInfo(aUri);
+  if (!info) {
+    return;
+  }
+
+  {
+    StaticMutexAutoLock lock(sMutex);
+    info->mRevoked = true;
+  }
+
+  if (aBroadcastToOtherProcesses &&
+      info->mObjectType == mozilla::dom::DataInfo::eBlobImpl) {
+    BroadcastBlobURLUnregistration(nsCString(aUri), info->mPrincipal);
+  }
+
+  // The timer will take care of removing the entry for real after
+  // RELEASING_TIMER milliseconds. In the meantime, the mozilla::dom::DataInfo,
+  // marked as revoked, will not be exposed.
+  ReleasingTimerHolder::Create(aUri);
+}
+
+/*static */
+bool BlobURLProtocolHandler::RemoveDataEntry(
+    const nsACString& aUri, nsIPrincipal* aPrincipal,
+    const Maybe<nsID>& aAgentClusterId) {
+  MOZ_ASSERT(NS_IsMainThread(), "changing gDataTable is main-thread only");
+  if (!gDataTable) {
+    return false;
+  }
+
+  mozilla::dom::DataInfo* info = GetDataInfo(aUri);
+  if (!info) {
+    return false;
+  }
+
+  if (!aPrincipal || !aPrincipal->Subsumes(info->mPrincipal)) {
+    return false;
+  }
+
+  if (StaticPrefs::privacy_partition_bloburl_per_agent_cluster() &&
+      aAgentClusterId.isSome() && info->mAgentClusterId.isSome() &&
+      !aAgentClusterId.value().Equals(info->mAgentClusterId.value())) {
+    return false;
+  }
+
+  RemoveDataEntry(aUri, true);
+  return true;
+}
+
+/* static */
+void BlobURLProtocolHandler::RemoveDataEntries() {
+  MOZ_ASSERT(NS_IsMainThread(), "changing gDataTable is main-thread only");
+  StaticMutexAutoLock lock(sMutex);
+  if (!gDataTable) {
+    return;
+  }
+
+  gDataTable->Clear();
+  delete gDataTable;
+  gDataTable = nullptr;
+}
+
+/* static */
+bool BlobURLProtocolHandler::HasDataEntry(const nsACString& aUri) {
+  MOZ_ASSERT(NS_IsMainThread(),
+             "without locking gDataTable is main-thread only");
+  return !!GetDataInfo(aUri);
+}
+
+/* static */
+nsresult BlobURLProtocolHandler::GenerateURIString(nsIPrincipal* aPrincipal,
+                                                   nsACString& aUri) {
+  nsresult rv;
+  nsCOMPtr<nsIUUIDGenerator> uuidgen =
+      do_GetService("@mozilla.org/uuid-generator;1", &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsID id;
+  rv = uuidgen->GenerateUUIDInPlace(&id);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  aUri.AssignLiteral(BLOBURI_SCHEME);
+  aUri.Append(':');
+
+  if (aPrincipal) {
+    nsAutoCString origin;
+    rv = aPrincipal->GetAsciiOrigin(origin);
+    if (NS_FAILED(rv)) {
+      origin.AssignLiteral("null");
+    }
+
+    aUri.Append(origin);
+    aUri.Append('/');
+  }
+
+  aUri += NSID_TrimBracketsASCII(id);
+
+  return NS_OK;
+}
+
+/* static */
+bool BlobURLProtocolHandler::GetDataEntry(
+    const nsACString& aUri, mozilla::dom::BlobImpl** aBlobImpl,
+    nsIPrincipal* aLoadingPrincipal, nsIPrincipal* aTriggeringPrincipal,
+    const OriginAttributes& aOriginAttributes, uint64_t aInnerWindowId,
+    const Maybe<nsID>& aAgentClusterId, bool aAlsoIfRevoked) {
+  MOZ_ASSERT(NS_IsMainThread(),
+             "without locking gDataTable is main-thread only");
+  MOZ_ASSERT(aTriggeringPrincipal);
+
+  if (!gDataTable) {
+    return false;
+  }
+
+  mozilla::dom::DataInfo* info = GetDataInfo(aUri, aAlsoIfRevoked);
+  if (!info) {
+    return false;
+  }
+
+  // We want to be sure that we stop the creation of the channel if the blob
+  // URL is copy-and-pasted on a different context (ex. private browsing or
+  // containers).
+  //
+  // We also allow the system principal to create the channel regardless of
+  // the OriginAttributes.  This is primarily for the benefit of mechanisms
+  // like the Download API that explicitly create a channel with the system
+  // principal and which is never mutated to have a non-zero
+  // mPrivateBrowsingId or container.
+
+  if ((NS_WARN_IF(!aLoadingPrincipal) ||
+       !aLoadingPrincipal->IsSystemPrincipal()) &&
+      NS_WARN_IF(!ChromeUtils::IsOriginAttributesEqualIgnoringFPD(
+          aOriginAttributes,
+          BasePrincipal::Cast(info->mPrincipal)->OriginAttributesRef()))) {
+    return false;
+  }
+
+  if (NS_WARN_IF(!aTriggeringPrincipal->Subsumes(info->mPrincipal))) {
+    return false;
+  }
+
+  // BlobURLs are openable on the same agent-cluster-id only.
+  if (StaticPrefs::privacy_partition_bloburl_per_agent_cluster() &&
+      aAgentClusterId.isSome() && info->mAgentClusterId.isSome() &&
+      NS_WARN_IF(!aAgentClusterId->Equals(info->mAgentClusterId.value()))) {
+    nsAutoString localizedMsg;
+    AutoTArray<nsString, 1> param;
+    CopyUTF8toUTF16(aUri, *param.AppendElement());
+    nsresult rv = nsContentUtils::FormatLocalizedString(
+        nsContentUtils::eDOM_PROPERTIES, "BlobDifferentClusterError", param,
+        localizedMsg);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return false;
+    }
+
+    nsContentUtils::ReportToConsoleByWindowID(
+        localizedMsg, nsIScriptError::errorFlag, "DOM"_ns, aInnerWindowId);
+    return false;
+  }
+
+  RefPtr<mozilla::dom::BlobImpl> blobImpl = info->mBlobImpl;
+  blobImpl.forget(aBlobImpl);
+
+  return true;
+}
+
+/* static */
+void BlobURLProtocolHandler::Traverse(
+    const nsACString& aUri, nsCycleCollectionTraversalCallback& aCallback) {
+  MOZ_ASSERT(NS_IsMainThread(),
+             "without locking gDataTable is main-thread only");
+  if (!gDataTable) {
+    return;
+  }
+
+  mozilla::dom::DataInfo* res;
+  gDataTable->Get(aUri, &res);
+  if (!res) {
+    return;
+  }
+
+  NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(
+      aCallback, "BlobURLProtocolHandler mozilla::dom::DataInfo.mBlobImpl");
+  aCallback.NoteXPCOMChild(res->mBlobImpl);
+
+  NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(
+      aCallback, "BlobURLProtocolHandler mozilla::dom::DataInfo.mMediaSource");
+  aCallback.NoteXPCOMChild(res->mMediaSource);
+}
+
+NS_IMPL_ISUPPORTS(BlobURLProtocolHandler, nsIProtocolHandler,
+                  nsISupportsWeakReference)
+
+/* static */ nsresult BlobURLProtocolHandler::CreateNewURI(
+    const nsACString& aSpec, const char* aCharset, nsIURI* aBaseURI,
+    nsIURI** aResult) {
+  *aResult = nullptr;
+
+  // This method can be called on any thread, which is why we lock the mutex
+  // for read access to gDataTable.
+  bool revoked = true;
+  {
+    StaticMutexAutoLock lock(sMutex);
+    mozilla::dom::DataInfo* info = GetDataInfo(aSpec);
+    if (info && info->mObjectType == mozilla::dom::DataInfo::eBlobImpl) {
+      revoked = info->mRevoked;
+    }
+  }
+
+  return NS_MutateURI(new BlobURL::Mutator())
+      .SetSpec(aSpec)
+      .Apply(&nsIBlobURLMutator::SetRevoked, revoked)
+      .Finalize(aResult);
+}
+
+NS_IMETHODIMP
+BlobURLProtocolHandler::NewChannel(nsIURI* aURI, nsILoadInfo* aLoadInfo,
+                                   nsIChannel** aResult) {
+  auto channel = MakeRefPtr<BlobURLChannel>(aURI, aLoadInfo);
+  channel.forget(aResult);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BlobURLProtocolHandler::AllowPort(int32_t port, const char* scheme,
+                                  bool* _retval) {
+  // don't override anything.
+  *_retval = false;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BlobURLProtocolHandler::GetScheme(nsACString& result) {
+  result.AssignLiteral(BLOBURI_SCHEME);
+  return NS_OK;
+}
+
+/* static */
+bool BlobURLProtocolHandler::GetBlobURLPrincipal(nsIURI* aURI,
+                                                 nsIPrincipal** aPrincipal) {
+  MOZ_ASSERT(aURI);
+  MOZ_ASSERT(aPrincipal);
+
+  RefPtr<BlobURL> blobURL;
+  nsresult rv =
+      aURI->QueryInterface(kHOSTOBJECTURICID, getter_AddRefs(blobURL));
+  if (NS_FAILED(rv) || !blobURL) {
+    return false;
+  }
+
+  StaticMutexAutoLock lock(sMutex);
+  mozilla::dom::DataInfo* info =
+      GetDataInfoFromURI(aURI, true /*aAlsoIfRevoked */);
+  if (!info || info->mObjectType != mozilla::dom::DataInfo::eBlobImpl ||
+      !info->mBlobImpl) {
+    return false;
+  }
+
+  nsCOMPtr<nsIPrincipal> principal;
+
+  if (blobURL->Revoked()) {
+    principal = NullPrincipal::Create(
+        BasePrincipal::Cast(info->mPrincipal)->OriginAttributesRef());
+  } else {
+    principal = info->mPrincipal;
+  }
+
+  principal.forget(aPrincipal);
+  return true;
+}
+
+bool BlobURLProtocolHandler::IsBlobURLBroadcastPrincipal(
+    nsIPrincipal* aPrincipal) {
+  return aPrincipal->IsSystemPrincipal() ||
+         aPrincipal->GetIsAddonOrExpandedAddonPrincipal();
+}
+
+}  // namespace dom
+}  // namespace mozilla
+
+nsresult NS_GetBlobForBlobURI(nsIURI* aURI, mozilla::dom::BlobImpl** aBlob) {
+  *aBlob = nullptr;
+  MOZ_ASSERT(NS_IsMainThread(),
+             "without locking gDataTable is main-thread only");
+  mozilla::dom::DataInfo* info =
+      mozilla::dom::GetDataInfoFromURI(aURI, false /* aAlsoIfRevoked */);
+  if (!info || info->mObjectType != mozilla::dom::DataInfo::eBlobImpl) {
+    return NS_ERROR_DOM_BAD_URI;
+  }
+
+  RefPtr<mozilla::dom::BlobImpl> blob = info->mBlobImpl;
+  blob.forget(aBlob);
+  return NS_OK;
+}
+
+nsresult NS_GetBlobForBlobURISpec(const nsACString& aSpec,
+                                  mozilla::dom::BlobImpl** aBlob,
+                                  bool aAlsoIfRevoked) {
+  *aBlob = nullptr;
+  MOZ_ASSERT(NS_IsMainThread(),
+             "without locking gDataTable is main-thread only");
+
+  mozilla::dom::DataInfo* info =
+      mozilla::dom::GetDataInfo(aSpec, aAlsoIfRevoked);
+  if (!info || info->mObjectType != mozilla::dom::DataInfo::eBlobImpl ||
+      !info->mBlobImpl) {
+    return NS_ERROR_DOM_BAD_URI;
+  }
+
+  RefPtr<mozilla::dom::BlobImpl> blob = info->mBlobImpl;
+  blob.forget(aBlob);
+  return NS_OK;
+}
+
+nsresult NS_GetSourceForMediaSourceURI(nsIURI* aURI,
+                                       mozilla::dom::MediaSource** aSource) {
+  *aSource = nullptr;
+
+  MOZ_ASSERT(NS_IsMainThread(),
+             "without locking gDataTable is main-thread only");
+  mozilla::dom::DataInfo* info = mozilla::dom::GetDataInfoFromURI(aURI);
+  if (!info || info->mObjectType != mozilla::dom::DataInfo::eMediaSource) {
+    return NS_ERROR_DOM_BAD_URI;
+  }
+
+  RefPtr<mozilla::dom::MediaSource> mediaSource = info->mMediaSource;
+  mediaSource.forget(aSource);
+  return NS_OK;
+}
+
+namespace mozilla::dom {
+
+bool IsType(nsIURI* aUri, mozilla::dom::DataInfo::ObjectType aType) {
+  // We lock because this may be called off-main-thread
+  StaticMutexAutoLock lock(sMutex);
+  mozilla::dom::DataInfo* info = GetDataInfoFromURI(aUri);
+  if (!info) {
+    return false;
+  }
+
+  return info->mObjectType == aType;
+}
+
+bool IsBlobURI(nsIURI* aUri) {
+  return IsType(aUri, mozilla::dom::DataInfo::eBlobImpl);
+}
+
+bool BlobURLSchemeIsHTTPOrHTTPS(const nsACString& aUri) {
+  return (StringBeginsWith(aUri, "blob:http://"_ns) ||
+          StringBeginsWith(aUri, "blob:https://"_ns));
+}
+
+bool IsMediaSourceURI(nsIURI* aUri) {
+  return IsType(aUri, mozilla::dom::DataInfo::eMediaSource);
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/file/uri/BlobURLProtocolHandler.h b/dom/file/uri/BlobURLProtocolHandler.h
new file mode 100644
index 0000000000..abb24f6fc0
--- /dev/null
+++ b/dom/file/uri/BlobURLProtocolHandler.h
@@ -0,0 +1,140 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_BlobURLProtocolHandler_h
+#define mozilla_dom_BlobURLProtocolHandler_h
+
+#include "mozilla/Attributes.h"
+#include "nsIProtocolHandler.h"
+#include "nsIURI.h"
+#include "nsCOMPtr.h"
+#include "nsTArray.h"
+#include "nsWeakReference.h"
+#include <functional>
+
+#define BLOBURI_SCHEME "blob"
+
+class nsIPrincipal;
+
+namespace mozilla {
+class BlobURLsReporter;
+class OriginAttributes;
+template <class T>
+class Maybe;
+
+namespace dom {
+
+class BlobImpl;
+class BlobURLRegistrationData;
+class ContentParent;
+class MediaSource;
+
+class BlobURLProtocolHandler final : public nsIProtocolHandler,
+                                     public nsSupportsWeakReference {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIPROTOCOLHANDLER
+
+  BlobURLProtocolHandler();
+
+  static nsresult CreateNewURI(const nsACString& aSpec, const char* aCharset,
+                               nsIURI* aBaseURI, nsIURI** result);
+
+  // Methods for managing uri->object mapping
+  // AddDataEntry creates the URI with the given scheme and returns it in aUri
+  static nsresult AddDataEntry(BlobImpl*, nsIPrincipal*,
+                               const Maybe<nsID>& aAgentClusterId,
+                               nsACString& aUri);
+  static nsresult AddDataEntry(MediaSource*, nsIPrincipal*,
+                               const Maybe<nsID>& aAgentClusterId,
+                               nsACString& aUri);
+  // IPC only
+  static void AddDataEntry(const nsACString& aURI, nsIPrincipal* aPrincipal,
+                           const Maybe<nsID>& aAgentClusterId,
+                           BlobImpl* aBlobImpl);
+
+  // These methods revoke a blobURL. Because some operations could still be in
+  // progress, the revoking consists in marking the blobURL as revoked and in
+  // removing it after RELEASING_TIMER milliseconds.
+  static void RemoveDataEntry(const nsACString& aUri,
+                              bool aBroadcastToOTherProcesses = true);
+  // Returns true if the entry was allowed to be removed.
+  static bool RemoveDataEntry(const nsACString& aUri, nsIPrincipal* aPrincipal,
+                              const Maybe<nsID>& aAgentClusterId);
+
+  static void RemoveDataEntries();
+
+  static bool HasDataEntry(const nsACString& aUri);
+
+  static bool GetDataEntry(const nsACString& aUri, BlobImpl** aBlobImpl,
+                           nsIPrincipal* aLoadingPrincipal,
+                           nsIPrincipal* aTriggeringPrincipal,
+                           const OriginAttributes& aOriginAttributes,
+                           uint64_t aInnerWindowId,
+                           const Maybe<nsID>& aAgentClusterId,
+                           bool aAlsoIfRevoked = false);
+
+  static void Traverse(const nsACString& aUri,
+                       nsCycleCollectionTraversalCallback& aCallback);
+
+  // Main-thread only method to invoke a helper function that gets called for
+  // every known and recently revoked Blob URL. The helper function should
+  // return true to keep going or false to stop enumerating (presumably because
+  // of an unexpected XPCOM or IPC error). This method returns false if already
+  // shutdown or if the helper method returns false, true otherwise.
+  static bool ForEachBlobURL(
+      std::function<bool(BlobImpl*, nsIPrincipal*, const Maybe<nsID>&,
+                         const nsACString&, bool aRevoked)>&& aCb);
+
+  // This method returns false if aURI is not a known BlobURL. Otherwise it
+  // returns true.
+  //
+  // When true is returned, the aPrincipal out param is meaningful.  It gets
+  // set to the principal that a channel loaded from the blob would get if
+  // the blob is not already revoked and to a NullPrincipal if the blob is
+  // revoked.
+  //
+  // This means that for a revoked blob URL this method may either return
+  // false or return true and hand out a NullPrincipal in aPrincipal,
+  // depending on whether the "remove it from the hashtable" timer has
+  // fired.  See RemoveDataEntry().
+  static bool GetBlobURLPrincipal(nsIURI* aURI, nsIPrincipal** aPrincipal);
+
+  // Check if metadata about Blob URLs created with this principal should be
+  // broadcast into every content process. This is currently the case for
+  // extension blob URLs and system principal blob URLs, as they can be loaded
+  // by system code and content scripts respectively.
+  static bool IsBlobURLBroadcastPrincipal(nsIPrincipal* aPrincipal);
+
+ private:
+  ~BlobURLProtocolHandler();
+
+  static void Init();
+
+  // If principal is not null, its origin will be used to generate the URI.
+  static nsresult GenerateURIString(nsIPrincipal* aPrincipal, nsACString& aUri);
+};
+
+bool IsBlobURI(nsIURI* aUri);
+bool IsMediaSourceURI(nsIURI* aUri);
+
+// Return true if inner scheme of blobURL is http or https, false otherwise.
+bool BlobURLSchemeIsHTTPOrHTTPS(const nsACString& aUri);
+
+}  // namespace dom
+}  // namespace mozilla
+
+extern nsresult NS_GetBlobForBlobURI(nsIURI* aURI,
+                                     mozilla::dom::BlobImpl** aBlob);
+
+extern nsresult NS_GetBlobForBlobURISpec(const nsACString& aSpec,
+                                         mozilla::dom::BlobImpl** aBlob,
+                                         bool aAlsoIfRevoked = false);
+
+extern nsresult NS_GetSourceForMediaSourceURI(
+    nsIURI* aURI, mozilla::dom::MediaSource** aSource);
+
+#endif /* mozilla_dom_BlobURLProtocolHandler_h */
diff --git a/dom/file/uri/FontTableURIProtocolHandler.cpp b/dom/file/uri/FontTableURIProtocolHandler.cpp
new file mode 100644
index 0000000000..d1db78239d
--- /dev/null
+++ b/dom/file/uri/FontTableURIProtocolHandler.cpp
@@ -0,0 +1,58 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "FontTableURIProtocolHandler.h"
+#include "nsIDUtils.h"
+#include "nsIUUIDGenerator.h"
+#include "nsNetUtil.h"
+#include "nsSimpleURI.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+/* static */
+nsresult FontTableURIProtocolHandler::GenerateURIString(nsACString& aUri) {
+  nsresult rv;
+  nsCOMPtr<nsIUUIDGenerator> uuidgen =
+      do_GetService("@mozilla.org/uuid-generator;1", &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsID id;
+  rv = uuidgen->GenerateUUIDInPlace(&id);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  aUri = FONTTABLEURI_SCHEME;
+  aUri.Append(':');
+
+  aUri += NSID_TrimBracketsASCII(id);
+
+  return NS_OK;
+}
+
+FontTableURIProtocolHandler::FontTableURIProtocolHandler() = default;
+FontTableURIProtocolHandler::~FontTableURIProtocolHandler() = default;
+
+NS_IMPL_ISUPPORTS(FontTableURIProtocolHandler, nsIProtocolHandler,
+                  nsISupportsWeakReference)
+
+NS_IMETHODIMP
+FontTableURIProtocolHandler::NewChannel(nsIURI* uri, nsILoadInfo* aLoadInfo,
+                                        nsIChannel** result) {
+  return NS_ERROR_DOM_BAD_URI;
+}
+
+NS_IMETHODIMP
+FontTableURIProtocolHandler::AllowPort(int32_t port, const char* scheme,
+                                       bool* _retval) {
+  *_retval = false;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+FontTableURIProtocolHandler::GetScheme(nsACString& result) {
+  result.AssignLiteral(FONTTABLEURI_SCHEME);
+  return NS_OK;
+}
diff --git a/dom/file/uri/FontTableURIProtocolHandler.h b/dom/file/uri/FontTableURIProtocolHandler.h
new file mode 100644
index 0000000000..fe2cea53ae
--- /dev/null
+++ b/dom/file/uri/FontTableURIProtocolHandler.h
@@ -0,0 +1,38 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef FontTableURIProtocolHandler_h
+#define FontTableURIProtocolHandler_h
+
+#include "nsIProtocolHandler.h"
+#include "nsIURI.h"
+#include "nsWeakReference.h"
+
+#define FONTTABLEURI_SCHEME "moz-fonttable"
+
+namespace mozilla::dom {
+
+class FontTableURIProtocolHandler final : public nsIProtocolHandler,
+                                          public nsSupportsWeakReference {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIPROTOCOLHANDLER
+
+  FontTableURIProtocolHandler();
+
+  static nsresult GenerateURIString(nsACString& aUri);
+
+ protected:
+  virtual ~FontTableURIProtocolHandler();
+};
+
+inline bool IsFontTableURI(nsIURI* aUri) {
+  return aUri->SchemeIs(FONTTABLEURI_SCHEME);
+}
+
+}  // namespace mozilla::dom
+
+#endif /* FontTableURIProtocolHandler_h */
diff --git a/dom/file/uri/components.conf b/dom/file/uri/components.conf
new file mode 100644
index 0000000000..30e62b2d62
--- /dev/null
+++ b/dom/file/uri/components.conf
@@ -0,0 +1,40 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+Classes = [
+    {
+        'cid': '{3fc8f04e-d719-43ca-9ad0-18ee320211f2}',
+        'contract_ids': ['@mozilla.org/network/protocol;1?name=moz-fonttable'],
+        'type': 'mozilla::dom::FontTableURIProtocolHandler',
+        'headers': ['mozilla/dom/FontTableURIProtocolHandler.h'],
+        'protocol_config': {
+            'scheme': 'moz-fonttable',
+            'flags': [
+                'URI_NORELATIVE',
+                'URI_NOAUTH',
+                'URI_LOADABLE_BY_SUBSUMERS',
+                'URI_NON_PERSISTABLE',
+                'URI_IS_LOCAL_RESOURCE',
+            ],
+        },
+    },
+    {
+        'cid': '{b43964aa-a078-44b2-b06b-fd4d1b172e66}',
+        'contract_ids': ['@mozilla.org/network/protocol;1?name=blob'],
+        'type': 'mozilla::dom::BlobURLProtocolHandler',
+        'headers': ['mozilla/dom/BlobURLProtocolHandler.h'],
+        'protocol_config': {
+            'scheme': 'blob',
+            'flags': [
+                'URI_NORELATIVE',
+                'URI_NOAUTH',
+                'URI_LOADABLE_BY_SUBSUMERS',
+                'URI_NON_PERSISTABLE',
+                'URI_IS_LOCAL_RESOURCE',
+            ],
+        },
+    },
+]
diff --git a/dom/file/uri/moz.build b/dom/file/uri/moz.build
new file mode 100644
index 0000000000..50fc404444
--- /dev/null
+++ b/dom/file/uri/moz.build
@@ -0,0 +1,36 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+with Files("**"):
+    BUG_COMPONENT = ("Core", "DOM: File")
+
+EXPORTS.mozilla.dom += [
+    "BlobURL.h",
+    "BlobURLInputStream.h",
+    "BlobURLProtocolHandler.h",
+    "FontTableURIProtocolHandler.h",
+]
+
+UNIFIED_SOURCES += [
+    "BlobURL.cpp",
+    "BlobURLChannel.cpp",
+    "BlobURLInputStream.cpp",
+    "BlobURLProtocolHandler.cpp",
+    "FontTableURIProtocolHandler.cpp",
+]
+
+XPCOM_MANIFESTS += [
+    "components.conf",
+]
+
+LOCAL_INCLUDES += [
+    "/dom/file",
+    "/netwerk/base",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"