Adding upstream version 124.0.1.upstream/124.0.1

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

58 files changed, 7245 insertions, 0 deletions

diff --git a/dom/filesystem/Directory.cpp b/dom/filesystem/Directory.cpp
new file mode 100644
index 0000000000..da5d6e5515
--- /dev/null
+++ b/dom/filesystem/Directory.cpp
@@ -0,0 +1,198 @@
+/* -*- 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/Directory.h"
+
+#include "GetDirectoryListingTask.h"
+#include "GetFilesTask.h"
+
+#include "nsIFile.h"
+#include "nsString.h"
+#include "mozilla/dom/BlobImpl.h"
+#include "mozilla/dom/DirectoryBinding.h"
+#include "mozilla/dom/FileSystemBase.h"
+#include "mozilla/dom/FileSystemUtils.h"
+#include "mozilla/dom/OSFileSystem.h"
+#include "mozilla/dom/WorkerPrivate.h"
+
+namespace mozilla::dom {
+
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(Directory)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(Directory)
+  if (tmp->mFileSystem) {
+    tmp->mFileSystem->Unlink();
+    tmp->mFileSystem = nullptr;
+  }
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mGlobal)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(Directory)
+  if (tmp->mFileSystem) {
+    tmp->mFileSystem->Traverse(cb);
+  }
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mGlobal)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(Directory)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(Directory)
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(Directory)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+/* static */
+already_AddRefed<Directory> Directory::Constructor(const GlobalObject& aGlobal,
+                                                   const nsAString& aRealPath,
+                                                   ErrorResult& aRv) {
+  nsCOMPtr<nsIFile> path;
+  aRv = NS_NewLocalFile(aRealPath, true, getter_AddRefs(path));
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(aGlobal.GetAsSupports());
+  if (NS_WARN_IF(!global)) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return nullptr;
+  }
+
+  return Create(global, path);
+}
+
+/* static */
+already_AddRefed<Directory> Directory::Create(nsIGlobalObject* aGlobal,
+                                              nsIFile* aFile,
+                                              FileSystemBase* aFileSystem) {
+  MOZ_ASSERT(aGlobal);
+  MOZ_ASSERT(aFile);
+
+  RefPtr<Directory> directory = new Directory(aGlobal, aFile, aFileSystem);
+  return directory.forget();
+}
+
+Directory::Directory(nsIGlobalObject* aGlobal, nsIFile* aFile,
+                     FileSystemBase* aFileSystem)
+    : mGlobal(aGlobal), mFile(aFile) {
+  MOZ_ASSERT(aFile);
+
+  // aFileSystem can be null. In this case we create a OSFileSystem when needed.
+  if (aFileSystem) {
+    // More likely, this is a OSFileSystem. This object keeps a reference of
+    // mGlobal but it's not cycle collectable and to avoid manual
+    // addref/release, it's better to have 1 object per directory. For this
+    // reason we clone it here.
+    mFileSystem = aFileSystem->Clone();
+  }
+}
+
+Directory::~Directory() = default;
+
+nsIGlobalObject* Directory::GetParentObject() const { return mGlobal; }
+
+JSObject* Directory::WrapObject(JSContext* aCx,
+                                JS::Handle<JSObject*> aGivenProto) {
+  return Directory_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+void Directory::GetName(nsAString& aRetval, ErrorResult& aRv) {
+  aRetval.Truncate();
+
+  RefPtr<FileSystemBase> fs = GetFileSystem(aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  fs->GetDirectoryName(mFile, aRetval, aRv);
+}
+
+void Directory::GetPath(nsAString& aRetval, ErrorResult& aRv) {
+  // This operation is expensive. Better to cache the result.
+  if (mPath.IsEmpty()) {
+    RefPtr<FileSystemBase> fs = GetFileSystem(aRv);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return;
+    }
+
+    fs->GetDOMPath(mFile, mPath, aRv);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return;
+    }
+  }
+
+  aRetval = mPath;
+}
+
+nsresult Directory::GetFullRealPath(nsAString& aPath) {
+  nsresult rv = mFile->GetPath(aPath);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+already_AddRefed<Promise> Directory::GetFilesAndDirectories(ErrorResult& aRv) {
+  RefPtr<FileSystemBase> fs = GetFileSystem(aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  RefPtr<GetDirectoryListingTaskChild> task =
+      GetDirectoryListingTaskChild::Create(fs, this, mFile, mFilters, aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  task->Start();
+
+  return task->GetPromise();
+}
+
+already_AddRefed<Promise> Directory::GetFiles(bool aRecursiveFlag,
+                                              ErrorResult& aRv) {
+  ErrorResult rv;
+  RefPtr<FileSystemBase> fs = GetFileSystem(rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    aRv.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
+    return nullptr;
+  }
+
+  RefPtr<GetFilesTaskChild> task =
+      GetFilesTaskChild::Create(fs, this, mFile, aRecursiveFlag, rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    aRv.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
+    return nullptr;
+  }
+
+  task->Start();
+
+  return task->GetPromise();
+}
+
+void Directory::SetContentFilters(const nsAString& aFilters) {
+  mFilters = aFilters;
+}
+
+FileSystemBase* Directory::GetFileSystem(ErrorResult& aRv) {
+  if (!mFileSystem) {
+    nsAutoString path;
+    aRv = mFile->GetPath(path);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return nullptr;
+    }
+
+    RefPtr<OSFileSystem> fs = new OSFileSystem(path);
+    fs->Init(mGlobal);
+
+    mFileSystem = fs;
+  }
+
+  return mFileSystem;
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/Directory.h b/dom/filesystem/Directory.h
new file mode 100644
index 0000000000..b8ee0e68e1
--- /dev/null
+++ b/dom/filesystem/Directory.h
@@ -0,0 +1,110 @@
+/* -*- 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_Directory_h
+#define mozilla_dom_Directory_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/File.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsWrapperCache.h"
+
+namespace mozilla {
+class ErrorResult;
+
+namespace dom {
+
+class FileSystemBase;
+class Promise;
+class StringOrFileOrDirectory;
+
+class Directory final : public nsISupports, public nsWrapperCache {
+ public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(Directory)
+
+  static already_AddRefed<Directory> Constructor(const GlobalObject& aGlobal,
+                                                 const nsAString& aRealPath,
+                                                 ErrorResult& aRv);
+
+  static already_AddRefed<Directory> Create(nsIGlobalObject* aGlobal,
+                                            nsIFile* aDirectory,
+                                            FileSystemBase* aFileSystem = 0);
+
+  // ========= Begin WebIDL bindings. ===========
+
+  nsIGlobalObject* GetParentObject() const;
+
+  virtual JSObject* WrapObject(JSContext* aCx,
+                               JS::Handle<JSObject*> aGivenProto) override;
+
+  void GetName(nsAString& aRetval, ErrorResult& aRv);
+
+  // From
+  // https://microsoftedge.github.io/directory-upload/proposal.html#directory-interface
+  // :
+
+  void GetPath(nsAString& aRetval, ErrorResult& aRv);
+
+  nsresult GetFullRealPath(nsAString& aPath);
+
+  already_AddRefed<Promise> GetFilesAndDirectories(ErrorResult& aRv);
+
+  already_AddRefed<Promise> GetFiles(bool aRecursiveFlag, ErrorResult& aRv);
+
+  // =========== End WebIDL bindings.============
+
+  /**
+   * Sets a semi-colon separated list of filters to filter-in or filter-out
+   * certain types of files when the contents of this directory are requested
+   * via a GetFilesAndDirectories() call.
+   *
+   * Currently supported keywords:
+   *
+   *   * filter-out-sensitive
+   *       This keyword filters out files or directories that we don't wish to
+   *       make available to Web content because we are concerned that there is
+   *       a risk that users may unwittingly give Web content access to them
+   *       and suffer undesirable consequences.  The details of what is
+   *       filtered out can be found in GetDirectoryListingTask::Work.
+   *
+   * In future, we will likely support filtering based on filename extensions
+   * (for example, aFilters could be "*.jpg; *.jpeg; *.gif"), but that isn't
+   * supported yet.  Once supported, files that don't match a specified
+   * extension (if any are specified) would be filtered out.  This
+   * functionality would allow us to apply the 'accept' attribute from
+   * <input type=file directory accept="..."> to the results of a directory
+   * picker operation.
+   */
+  void SetContentFilters(const nsAString& aFilters);
+
+  FileSystemBase* GetFileSystem(ErrorResult& aRv);
+
+  nsIFile* GetInternalNsIFile() const { return mFile; }
+
+ private:
+  Directory(nsIGlobalObject* aGlobal, nsIFile* aFile,
+            FileSystemBase* aFileSystem = nullptr);
+  ~Directory();
+
+  /*
+   * Convert relative DOM path to the absolute real path.
+   */
+  nsresult DOMPathToRealPath(const nsAString& aPath, nsIFile** aFile) const;
+
+  nsCOMPtr<nsIGlobalObject> mGlobal;
+  RefPtr<FileSystemBase> mFileSystem;
+  nsCOMPtr<nsIFile> mFile;
+
+  nsString mFilters;
+  nsString mPath;
+};
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // mozilla_dom_Directory_h
diff --git a/dom/filesystem/FileSystemBase.cpp b/dom/filesystem/FileSystemBase.cpp
new file mode 100644
index 0000000000..776ecc9db5
--- /dev/null
+++ b/dom/filesystem/FileSystemBase.cpp
@@ -0,0 +1,143 @@
+/* -*- 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/FileSystemBase.h"
+
+#include "mozilla/ErrorResult.h"
+#include "mozilla/dom/BlobImpl.h"
+#include "mozilla/dom/FileSystemUtils.h"
+#include "nsIFile.h"
+#include "OSFileSystem.h"
+
+namespace mozilla::dom {
+
+FileSystemBase::FileSystemBase() : mShutdown(false) {}
+
+FileSystemBase::~FileSystemBase() { AssertIsOnOwningThread(); }
+
+void FileSystemBase::Shutdown() {
+  AssertIsOnOwningThread();
+  mShutdown = true;
+}
+
+nsIGlobalObject* FileSystemBase::GetParentObject() const {
+  AssertIsOnOwningThread();
+  return nullptr;
+}
+
+bool FileSystemBase::GetRealPath(BlobImpl* aFile, nsIFile** aPath) const {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(aFile, "aFile Should not be null.");
+  MOZ_ASSERT(aPath);
+
+  nsAutoString filePath;
+  ErrorResult rv;
+  aFile->GetMozFullPathInternal(filePath, rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    rv.SuppressException();
+    return false;
+  }
+
+  rv = NS_NewLocalFile(filePath, true, aPath);
+  if (NS_WARN_IF(rv.Failed())) {
+    rv.SuppressException();
+    return false;
+  }
+
+  return true;
+}
+
+bool FileSystemBase::IsSafeFile(nsIFile* aFile) const {
+  AssertIsOnOwningThread();
+  return false;
+}
+
+bool FileSystemBase::IsSafeDirectory(Directory* aDir) const {
+  AssertIsOnOwningThread();
+  return false;
+}
+
+void FileSystemBase::GetDirectoryName(nsIFile* aFile, nsAString& aRetval,
+                                      ErrorResult& aRv) const {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(aFile);
+
+  aRv = aFile->GetLeafName(aRetval);
+  NS_WARNING_ASSERTION(!aRv.Failed(), "GetLeafName failed");
+}
+
+void FileSystemBase::GetDOMPath(nsIFile* aFile, nsAString& aRetval,
+                                ErrorResult& aRv) const {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(aFile);
+
+  aRetval.Truncate();
+
+  nsCOMPtr<nsIFile> fileSystemPath;
+  aRv = NS_NewLocalFile(LocalRootPath(), true, getter_AddRefs(fileSystemPath));
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  nsCOMPtr<nsIFile> path;
+  aRv = aFile->Clone(getter_AddRefs(path));
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  nsTArray<nsString> parts;
+
+  while (true) {
+    nsAutoString leafName;
+    aRv = path->GetLeafName(leafName);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return;
+    }
+
+    if (!leafName.IsEmpty()) {
+      parts.AppendElement(leafName);
+    }
+
+    bool equal = false;
+    aRv = fileSystemPath->Equals(path, &equal);
+    if (NS_WARN_IF(aRv.Failed())) {
+      return;
+    }
+
+    if (equal) {
+      break;
+    }
+
+    nsCOMPtr<nsIFile> parentPath;
+    aRv = path->GetParent(getter_AddRefs(parentPath));
+    if (NS_WARN_IF(aRv.Failed())) {
+      return;
+    }
+
+    MOZ_ASSERT(parentPath);
+
+    aRv = parentPath->Clone(getter_AddRefs(path));
+    if (NS_WARN_IF(aRv.Failed())) {
+      return;
+    }
+  }
+
+  if (parts.IsEmpty()) {
+    aRetval.AppendLiteral(FILESYSTEM_DOM_PATH_SEPARATOR_LITERAL);
+    return;
+  }
+
+  for (int32_t i = parts.Length() - 1; i >= 0; --i) {
+    aRetval.AppendLiteral(FILESYSTEM_DOM_PATH_SEPARATOR_LITERAL);
+    aRetval.Append(parts[i]);
+  }
+}
+
+void FileSystemBase::AssertIsOnOwningThread() const {
+  NS_ASSERT_OWNINGTHREAD(FileSystemBase);
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/FileSystemBase.h b/dom/filesystem/FileSystemBase.h
new file mode 100644
index 0000000000..b78fe1736b
--- /dev/null
+++ b/dom/filesystem/FileSystemBase.h
@@ -0,0 +1,80 @@
+/* -*- 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_FileSystemBase_h
+#define mozilla_dom_FileSystemBase_h
+
+#include "nsString.h"
+#include "Directory.h"
+
+namespace mozilla::dom {
+
+class BlobImpl;
+
+class FileSystemBase {
+ public:
+  NS_INLINE_DECL_REFCOUNTING(FileSystemBase)
+
+  FileSystemBase();
+
+  virtual void Shutdown();
+
+  // SerializeDOMPath the FileSystem to string.
+  virtual void SerializeDOMPath(nsAString& aOutput) const = 0;
+
+  virtual already_AddRefed<FileSystemBase> Clone() = 0;
+
+  virtual bool ShouldCreateDirectory() = 0;
+
+  virtual nsIGlobalObject* GetParentObject() const;
+
+  virtual void GetDirectoryName(nsIFile* aFile, nsAString& aRetval,
+                                ErrorResult& aRv) const;
+
+  void GetDOMPath(nsIFile* aFile, nsAString& aRetval, ErrorResult& aRv) const;
+
+  /*
+   * Return the local root path of the FileSystem implementation.
+   * For OSFileSystem, this is equal to the path of the root Directory;
+   * For DeviceStorageFileSystem, this is the path of the SDCard, parent
+   * directory of the exposed root Directory (per type).
+   */
+  const nsAString& LocalRootPath() const { return mLocalRootPath; }
+
+  bool IsShutdown() const { return mShutdown; }
+
+  virtual bool IsSafeFile(nsIFile* aFile) const;
+
+  virtual bool IsSafeDirectory(Directory* aDir) const;
+
+  bool GetRealPath(BlobImpl* aFile, nsIFile** aPath) const;
+
+  // CC methods
+  virtual void Unlink() {}
+  virtual void Traverse(nsCycleCollectionTraversalCallback& cb) {}
+
+  void AssertIsOnOwningThread() const;
+
+ protected:
+  virtual ~FileSystemBase();
+
+  // The local path of the root (i.e. the OS path, with OS path separators, of
+  // the OS directory that acts as the root of this OSFileSystem).
+  // This path must be set by the FileSystem implementation immediately
+  // because it will be used for the validation of any FileSystemTaskChildBase.
+  // The concept of this path is that, any task will never go out of it and this
+  // must be considered the OS 'root' of the current FileSystem. Different
+  // Directory object can have different OS 'root' path.
+  // To be more clear, any path managed by this FileSystem implementation must
+  // be discendant of this local root path.
+  nsString mLocalRootPath;
+
+  bool mShutdown;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_FileSystemBase_h
diff --git a/dom/filesystem/FileSystemRequestParent.cpp b/dom/filesystem/FileSystemRequestParent.cpp
new file mode 100644
index 0000000000..25211dbd23
--- /dev/null
+++ b/dom/filesystem/FileSystemRequestParent.cpp
@@ -0,0 +1,188 @@
+/* -*- 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/FileSystemRequestParent.h"
+#include "mozilla/dom/PFileSystemParams.h"
+
+#include "GetDirectoryListingTask.h"
+#include "GetFileOrDirectoryTask.h"
+#include "GetFilesTask.h"
+
+#include "mozilla/dom/BlobImpl.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/FileSystemBase.h"
+#include "mozilla/dom/FileSystemSecurity.h"
+#include "mozilla/ipc/BackgroundParent.h"
+#include "mozilla/dom/OSFileSystem.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/Unused.h"
+#include "nsProxyRelease.h"
+
+using namespace mozilla::ipc;
+
+namespace mozilla::dom {
+
+FileSystemRequestParent::FileSystemRequestParent() : mDestroyed(false) {
+  AssertIsOnBackgroundThread();
+}
+
+FileSystemRequestParent::~FileSystemRequestParent() {
+  AssertIsOnBackgroundThread();
+}
+
+#define FILESYSTEM_REQUEST_PARENT_DISPATCH_ENTRY(name)          \
+  case FileSystemParams::TFileSystem##name##Params: {           \
+    const FileSystem##name##Params& p = aParams;                \
+    mFileSystem = new OSFileSystemParent(p.filesystem());       \
+    MOZ_ASSERT(mFileSystem);                                    \
+    mTask = name##TaskParent::Create(mFileSystem, p, this, rv); \
+    if (NS_WARN_IF(rv.Failed())) {                              \
+      rv.SuppressException();                                   \
+      return false;                                             \
+    }                                                           \
+    break;                                                      \
+  }
+
+bool FileSystemRequestParent::Initialize(const FileSystemParams& aParams) {
+  AssertIsOnBackgroundThread();
+
+  ErrorResult rv;
+
+  switch (aParams.type()) {
+    FILESYSTEM_REQUEST_PARENT_DISPATCH_ENTRY(GetDirectoryListing)
+    FILESYSTEM_REQUEST_PARENT_DISPATCH_ENTRY(GetFileOrDirectory)
+    FILESYSTEM_REQUEST_PARENT_DISPATCH_ENTRY(GetFiles)
+
+    default: {
+      MOZ_CRASH("not reached");
+      break;
+    }
+  }
+
+  if (NS_WARN_IF(!mTask || !mFileSystem)) {
+    // Should never reach here.
+    return false;
+  }
+
+  return true;
+}
+
+namespace {
+
+class CheckPermissionRunnable final : public Runnable {
+ public:
+  CheckPermissionRunnable(
+      already_AddRefed<ThreadsafeContentParentHandle> aParent,
+      FileSystemRequestParent* aActor, FileSystemTaskParentBase* aTask,
+      const nsAString& aPath)
+      : Runnable("dom::CheckPermissionRunnable"),
+        mContentHandle(aParent),
+        mActor(aActor),
+        mTask(aTask),
+        mPath(aPath),
+        mBackgroundEventTarget(GetCurrentSerialEventTarget()) {
+    AssertIsInMainProcess();
+    AssertIsOnBackgroundThread();
+
+    MOZ_ASSERT(mContentHandle);
+    MOZ_ASSERT(mActor);
+    MOZ_ASSERT(mTask);
+    MOZ_ASSERT(mBackgroundEventTarget);
+  }
+
+  NS_IMETHOD
+  Run() override {
+    if (NS_IsMainThread()) {
+      if (!mozilla::Preferences::GetBool("dom.filesystem.pathcheck.disabled",
+                                         false)) {
+        RefPtr<FileSystemSecurity> fss = FileSystemSecurity::Get();
+        if (NS_WARN_IF(!fss || !fss->ContentProcessHasAccessTo(
+                                   mContentHandle->ChildID(), mPath))) {
+          AssertIsOnMainThread();
+          if (RefPtr<ContentParent> contentParent =
+                  mContentHandle->GetContentParent()) {
+            contentParent->KillHard("This path is not allowed.");
+          }
+          return NS_OK;
+        }
+      }
+
+      return mBackgroundEventTarget->Dispatch(this, NS_DISPATCH_NORMAL);
+    }
+
+    AssertIsOnBackgroundThread();
+
+    // It can happen that this actor has been destroyed in the meantime we were
+    // on the main-thread.
+    if (!mActor->Destroyed()) {
+      mTask->Start();
+    }
+
+    return NS_OK;
+  }
+
+ private:
+  ~CheckPermissionRunnable() {
+    NS_ProxyRelease("CheckPermissionRunnable::mActor", mBackgroundEventTarget,
+                    mActor.forget());
+  }
+
+  RefPtr<ThreadsafeContentParentHandle> mContentHandle;
+  RefPtr<FileSystemRequestParent> mActor;
+  RefPtr<FileSystemTaskParentBase> mTask;
+  const nsString mPath;
+
+  nsCOMPtr<nsIEventTarget> mBackgroundEventTarget;
+};
+
+}  // namespace
+
+void FileSystemRequestParent::Start() {
+  AssertIsInMainProcess();
+  AssertIsOnBackgroundThread();
+
+  MOZ_ASSERT(!mDestroyed);
+  MOZ_ASSERT(mFileSystem);
+  MOZ_ASSERT(mTask);
+
+  nsAutoString path;
+  if (NS_WARN_IF(NS_FAILED(mTask->GetTargetPath(path)))) {
+    (void)Send__delete__(this,
+                         FileSystemErrorResponse(NS_ERROR_DOM_SECURITY_ERR));
+    return;
+  }
+
+  RefPtr<ThreadsafeContentParentHandle> parent =
+      BackgroundParent::GetContentParentHandle(Manager());
+
+  // If the ThreadsafeContentParentHandle is null we are dealing with a
+  // same-process actor.
+  if (!parent) {
+    mTask->Start();
+    return;
+  }
+
+  RefPtr<Runnable> runnable =
+      new CheckPermissionRunnable(parent.forget(), this, mTask, path);
+  NS_DispatchToMainThread(runnable);
+}
+
+void FileSystemRequestParent::ActorDestroy(ActorDestroyReason aWhy) {
+  AssertIsOnBackgroundThread();
+  MOZ_ASSERT(!mDestroyed);
+
+  if (!mFileSystem) {
+    return;
+  }
+
+  mFileSystem->Shutdown();
+  mFileSystem = nullptr;
+  mTask = nullptr;
+  mDestroyed = true;
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/FileSystemRequestParent.h b/dom/filesystem/FileSystemRequestParent.h
new file mode 100644
index 0000000000..7ac1547d27
--- /dev/null
+++ b/dom/filesystem/FileSystemRequestParent.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_FileSystemRequestParent_h
+#define mozilla_dom_FileSystemRequestParent_h
+
+#include "mozilla/dom/PFileSystemRequestParent.h"
+#include "mozilla/dom/FileSystemBase.h"
+
+namespace mozilla::dom {
+
+class FileSystemParams;
+class FileSystemTaskParentBase;
+
+class FileSystemRequestParent final : public PFileSystemRequestParent {
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(FileSystemRequestParent, final)
+
+ public:
+  FileSystemRequestParent();
+
+  bool Initialize(const FileSystemParams& aParams);
+
+  void Start();
+
+  bool Destroyed() const { return mDestroyed; }
+
+  virtual void ActorDestroy(ActorDestroyReason why) override;
+
+ private:
+  ~FileSystemRequestParent();
+
+  RefPtr<FileSystemBase> mFileSystem;
+  RefPtr<FileSystemTaskParentBase> mTask;
+
+  bool mDestroyed;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_FileSystemRequestParent_h
diff --git a/dom/filesystem/FileSystemSecurity.cpp b/dom/filesystem/FileSystemSecurity.cpp
new file mode 100644
index 0000000000..b9468270d4
--- /dev/null
+++ b/dom/filesystem/FileSystemSecurity.cpp
@@ -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/. */
+
+#include "FileSystemSecurity.h"
+#include "FileSystemUtils.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/ipc/BackgroundParent.h"
+#include "mozilla/StaticPtr.h"
+
+namespace mozilla::dom {
+
+namespace {
+
+StaticRefPtr<FileSystemSecurity> gFileSystemSecurity;
+
+}  // namespace
+
+/* static */
+already_AddRefed<FileSystemSecurity> FileSystemSecurity::Get() {
+  MOZ_ASSERT(NS_IsMainThread());
+  mozilla::ipc::AssertIsInMainProcess();
+
+  RefPtr<FileSystemSecurity> service = gFileSystemSecurity.get();
+  return service.forget();
+}
+
+/* static */
+already_AddRefed<FileSystemSecurity> FileSystemSecurity::GetOrCreate() {
+  MOZ_ASSERT(NS_IsMainThread());
+  mozilla::ipc::AssertIsInMainProcess();
+
+  if (!gFileSystemSecurity) {
+    gFileSystemSecurity = new FileSystemSecurity();
+    ClearOnShutdown(&gFileSystemSecurity);
+  }
+
+  RefPtr<FileSystemSecurity> service = gFileSystemSecurity.get();
+  return service.forget();
+}
+
+FileSystemSecurity::FileSystemSecurity() {
+  MOZ_ASSERT(NS_IsMainThread());
+  mozilla::ipc::AssertIsInMainProcess();
+}
+
+FileSystemSecurity::~FileSystemSecurity() {
+  MOZ_ASSERT(NS_IsMainThread());
+  mozilla::ipc::AssertIsInMainProcess();
+}
+
+void FileSystemSecurity::GrantAccessToContentProcess(
+    ContentParentId aId, const nsAString& aDirectoryPath) {
+  MOZ_ASSERT(NS_IsMainThread());
+  mozilla::ipc::AssertIsInMainProcess();
+
+  mPaths.WithEntryHandle(aId, [&](auto&& entry) {
+    if (entry && entry.Data()->Contains(aDirectoryPath)) {
+      return;
+    }
+
+    entry.OrInsertWith([] { return MakeUnique<nsTArray<nsString>>(); })
+        ->AppendElement(aDirectoryPath);
+  });
+}
+
+void FileSystemSecurity::Forget(ContentParentId aId) {
+  MOZ_ASSERT(NS_IsMainThread());
+  mozilla::ipc::AssertIsInMainProcess();
+
+  mPaths.Remove(aId);
+}
+
+bool FileSystemSecurity::ContentProcessHasAccessTo(ContentParentId aId,
+                                                   const nsAString& aPath) {
+  MOZ_ASSERT(NS_IsMainThread());
+  mozilla::ipc::AssertIsInMainProcess();
+
+#if defined(XP_WIN)
+  if (StringBeginsWith(aPath, u"..\\"_ns) ||
+      FindInReadable(u"\\..\\"_ns, aPath)) {
+    return false;
+  }
+#elif defined(XP_UNIX)
+  if (StringBeginsWith(aPath, u"../"_ns) || FindInReadable(u"/../"_ns, aPath)) {
+    return false;
+  }
+#endif
+
+  nsTArray<nsString>* paths;
+  if (!mPaths.Get(aId, &paths)) {
+    return false;
+  }
+
+  for (uint32_t i = 0, len = paths->Length(); i < len; ++i) {
+    if (FileSystemUtils::IsDescendantPath(paths->ElementAt(i), aPath)) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/FileSystemSecurity.h b/dom/filesystem/FileSystemSecurity.h
new file mode 100644
index 0000000000..381d156777
--- /dev/null
+++ b/dom/filesystem/FileSystemSecurity.h
@@ -0,0 +1,40 @@
+/* -*- 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_FileSystemSecurity_h
+#define mozilla_dom_FileSystemSecurity_h
+
+#include "mozilla/dom/ipc/IdType.h"
+#include "nsClassHashtable.h"
+#include "nsISupportsImpl.h"
+
+namespace mozilla::dom {
+
+class FileSystemSecurity final {
+ public:
+  NS_INLINE_DECL_REFCOUNTING(FileSystemSecurity)
+
+  static already_AddRefed<FileSystemSecurity> Get();
+
+  static already_AddRefed<FileSystemSecurity> GetOrCreate();
+
+  void GrantAccessToContentProcess(ContentParentId aId,
+                                   const nsAString& aDirectoryPath);
+
+  void Forget(ContentParentId aId);
+
+  bool ContentProcessHasAccessTo(ContentParentId aId, const nsAString& aPath);
+
+ private:
+  FileSystemSecurity();
+  ~FileSystemSecurity();
+
+  nsClassHashtable<nsUint64HashKey, nsTArray<nsString>> mPaths;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_FileSystemSecurity_h
diff --git a/dom/filesystem/FileSystemTaskBase.cpp b/dom/filesystem/FileSystemTaskBase.cpp
new file mode 100644
index 0000000000..34cfd8f018
--- /dev/null
+++ b/dom/filesystem/FileSystemTaskBase.cpp
@@ -0,0 +1,246 @@
+/* -*- 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/FileSystemTaskBase.h"
+
+#include "nsNetCID.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/dom/FileSystemBase.h"
+#include "mozilla/dom/FileSystemRequestParent.h"
+#include "mozilla/dom/FileSystemUtils.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/ipc/BackgroundChild.h"
+#include "mozilla/ipc/BackgroundParent.h"
+#include "mozilla/ipc/PBackgroundChild.h"
+#include "mozilla/Unused.h"
+#include "nsProxyRelease.h"
+
+namespace mozilla::dom {
+
+namespace {
+
+nsresult FileSystemErrorFromNsError(const nsresult& aErrorValue) {
+  uint16_t module = NS_ERROR_GET_MODULE(aErrorValue);
+  if (module == NS_ERROR_MODULE_DOM_FILESYSTEM ||
+      module == NS_ERROR_MODULE_DOM_FILE || module == NS_ERROR_MODULE_DOM) {
+    return aErrorValue;
+  }
+
+  switch (aErrorValue) {
+    case NS_OK:
+      return NS_OK;
+
+    case NS_ERROR_FILE_INVALID_PATH:
+    case NS_ERROR_FILE_UNRECOGNIZED_PATH:
+      return NS_ERROR_DOM_FILESYSTEM_INVALID_PATH_ERR;
+
+    case NS_ERROR_FILE_DESTINATION_NOT_DIR:
+      return NS_ERROR_DOM_FILESYSTEM_INVALID_MODIFICATION_ERR;
+
+    case NS_ERROR_FILE_ACCESS_DENIED:
+    case NS_ERROR_FILE_DIR_NOT_EMPTY:
+      return NS_ERROR_DOM_FILESYSTEM_NO_MODIFICATION_ALLOWED_ERR;
+
+    case NS_ERROR_FILE_NOT_FOUND:
+    case NS_ERROR_NOT_AVAILABLE:
+      return NS_ERROR_DOM_FILE_NOT_FOUND_ERR;
+
+    case NS_ERROR_FILE_ALREADY_EXISTS:
+      return NS_ERROR_DOM_FILESYSTEM_PATH_EXISTS_ERR;
+
+    case NS_ERROR_FILE_NOT_DIRECTORY:
+      return NS_ERROR_DOM_FILESYSTEM_TYPE_MISMATCH_ERR;
+
+    case NS_ERROR_UNEXPECTED:
+    default:
+      return NS_ERROR_DOM_FILESYSTEM_UNKNOWN_ERR;
+  }
+}
+
+nsresult DispatchToIOThread(nsIRunnable* aRunnable) {
+  MOZ_ASSERT(aRunnable);
+
+  nsCOMPtr<nsIEventTarget> target =
+      do_GetService(NS_STREAMTRANSPORTSERVICE_CONTRACTID);
+  MOZ_ASSERT(target);
+
+  return target->Dispatch(aRunnable, NS_DISPATCH_NORMAL);
+}
+
+}  // anonymous namespace
+
+/**
+ * FileSystemTaskBase class
+ */
+
+FileSystemTaskChildBase::FileSystemTaskChildBase(nsIGlobalObject* aGlobalObject,
+                                                 FileSystemBase* aFileSystem)
+    : mErrorValue(NS_OK),
+      mFileSystem(aFileSystem),
+      mGlobalObject(aGlobalObject) {
+  MOZ_ASSERT(aFileSystem, "aFileSystem should not be null.");
+  aFileSystem->AssertIsOnOwningThread();
+  MOZ_ASSERT(aGlobalObject);
+}
+
+FileSystemTaskChildBase::~FileSystemTaskChildBase() {
+  mFileSystem->AssertIsOnOwningThread();
+}
+
+FileSystemBase* FileSystemTaskChildBase::GetFileSystem() const {
+  mFileSystem->AssertIsOnOwningThread();
+  return mFileSystem.get();
+}
+
+void FileSystemTaskChildBase::Start() {
+  mFileSystem->AssertIsOnOwningThread();
+
+  mozilla::ipc::PBackgroundChild* actor =
+      mozilla::ipc::BackgroundChild::GetOrCreateForCurrentThread();
+  if (NS_WARN_IF(!actor)) {
+    // We are probably shutting down.
+    return;
+  }
+
+  nsAutoString serialization;
+  mFileSystem->SerializeDOMPath(serialization);
+
+  ErrorResult rv;
+  FileSystemParams params = GetRequestParams(serialization, rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    rv.SuppressException();
+    return;
+  }
+
+  actor->SendPFileSystemRequestConstructor(this, params);
+}
+
+void FileSystemTaskChildBase::SetRequestResult(
+    const FileSystemResponseValue& aValue) {
+  mFileSystem->AssertIsOnOwningThread();
+
+  if (aValue.type() == FileSystemResponseValue::TFileSystemErrorResponse) {
+    FileSystemErrorResponse r = aValue;
+    mErrorValue = r.error();
+  } else {
+    ErrorResult rv;
+    SetSuccessRequestResult(aValue, rv);
+    mErrorValue = rv.StealNSResult();
+  }
+}
+
+mozilla::ipc::IPCResult FileSystemTaskChildBase::Recv__delete__(
+    const FileSystemResponseValue& aValue) {
+  mFileSystem->AssertIsOnOwningThread();
+
+  SetRequestResult(aValue);
+  HandlerCallback();
+  return IPC_OK();
+}
+
+void FileSystemTaskChildBase::SetError(const nsresult& aErrorValue) {
+  mErrorValue = FileSystemErrorFromNsError(aErrorValue);
+}
+
+/**
+ * FileSystemTaskParentBase class
+ */
+
+FileSystemTaskParentBase::FileSystemTaskParentBase(
+    FileSystemBase* aFileSystem, const FileSystemParams& aParam,
+    FileSystemRequestParent* aParent)
+    : Runnable("dom::FileSystemTaskParentBase"),
+      mErrorValue(NS_OK),
+      mFileSystem(aFileSystem),
+      mRequestParent(aParent),
+      mBackgroundEventTarget(GetCurrentSerialEventTarget()) {
+  MOZ_ASSERT(XRE_IsParentProcess(), "Only call from parent process!");
+  MOZ_ASSERT(aFileSystem, "aFileSystem should not be null.");
+  MOZ_ASSERT(aParent);
+  MOZ_ASSERT(mBackgroundEventTarget);
+  mozilla::ipc::AssertIsOnBackgroundThread();
+}
+
+FileSystemTaskParentBase::~FileSystemTaskParentBase() {
+  // This task can be released on different threads because we dispatch it (as
+  // runnable) to main-thread, I/O and then back to the PBackground thread.
+  NS_ProxyRelease("FileSystemTaskParentBase::mFileSystem",
+                  mBackgroundEventTarget, mFileSystem.forget());
+  NS_ProxyRelease("FileSystemTaskParentBase::mRequestParent",
+                  mBackgroundEventTarget, mRequestParent.forget());
+}
+
+void FileSystemTaskParentBase::Start() {
+  mozilla::ipc::AssertIsOnBackgroundThread();
+  mFileSystem->AssertIsOnOwningThread();
+
+  DebugOnly<nsresult> rv = DispatchToIOThread(this);
+  NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "DispatchToIOThread failed");
+}
+
+void FileSystemTaskParentBase::HandleResult() {
+  mozilla::ipc::AssertIsOnBackgroundThread();
+  mFileSystem->AssertIsOnOwningThread();
+
+  if (mFileSystem->IsShutdown()) {
+    return;
+  }
+
+  MOZ_ASSERT(mRequestParent);
+  (void)mRequestParent->Send__delete__(mRequestParent, GetRequestResult());
+}
+
+FileSystemResponseValue FileSystemTaskParentBase::GetRequestResult() const {
+  mozilla::ipc::AssertIsOnBackgroundThread();
+  mFileSystem->AssertIsOnOwningThread();
+
+  if (HasError()) {
+    return FileSystemErrorResponse(mErrorValue);
+  }
+
+  ErrorResult rv;
+  FileSystemResponseValue value = GetSuccessRequestResult(rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    return FileSystemErrorResponse(rv.StealNSResult());
+  }
+
+  return value;
+}
+
+void FileSystemTaskParentBase::SetError(const nsresult& aErrorValue) {
+  mErrorValue = FileSystemErrorFromNsError(aErrorValue);
+}
+
+NS_IMETHODIMP
+FileSystemTaskParentBase::Run() {
+  // This method can run in 2 different threads. Here why:
+  // 1. We are are on the I/O thread and we call IOWork().
+  // 2. After step 1, it returns back to the PBackground thread.
+
+  // Run I/O thread tasks
+  if (!mozilla::ipc::IsOnBackgroundThread()) {
+    nsresult rv = IOWork();
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      SetError(rv);
+    }
+
+    // Let's go back to PBackground thread to finish the work.
+    rv = mBackgroundEventTarget->Dispatch(this, NS_DISPATCH_NORMAL);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    return NS_OK;
+  }
+
+  // If we are here, it's because the I/O work has been done and we have to
+  // handle the result back via IPC.
+  mozilla::ipc::AssertIsOnBackgroundThread();
+  HandleResult();
+  return NS_OK;
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/FileSystemTaskBase.h b/dom/filesystem/FileSystemTaskBase.h
new file mode 100644
index 0000000000..3d440403cc
--- /dev/null
+++ b/dom/filesystem/FileSystemTaskBase.h
@@ -0,0 +1,254 @@
+/* -*- 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_FileSystemTaskBase_h
+#define mozilla_dom_FileSystemTaskBase_h
+
+#include "mozilla/dom/FileSystemRequestParent.h"
+#include "mozilla/dom/PFileSystemRequestChild.h"
+#include "nsIGlobalObject.h"
+#include "nsThreadUtils.h"
+
+namespace mozilla {
+class ErrorResult;
+
+namespace dom {
+
+class BlobImpl;
+class FileSystemBase;
+class FileSystemParams;
+
+/*
+ * The base class to implement a Task class.
+ * The file system operations can only be performed in the parent process. In
+ * order to avoid duplicated code, we used PBackground for child-parent and
+ * parent-parent communications.
+ *
+ * The following diagram illustrates the how a API call from the content page
+ * starts a task and gets call back results.
+ *
+ * The left block is the call sequence inside any process loading content, while
+ * the right block is the call sequence only inside the parent process.
+ *
+ *       Page
+ *        |
+ *        | (1)
+ *  ______|_________________________     |    _________________________________
+ * |      |                          |   |   |                                 |
+ * |      |                          |   |   |                                 |
+ * |      V                          |  IPC  | PBackground thread on           |
+ * | [new FileSystemTaskChildBase()] |   |   | the parent process              |
+ * |         |                       |   |   |                                 |
+ * |         | (2)                   |       |                                 |
+ * |         V                       |  (3)  |                                 |
+ * |    [GetRequestParams]------------------->[new FileSystemTaskParentBase()] |
+ * |                                 |       |          |                      |
+ * |                                 |   |   |          | (4)   _____________  |
+ * |                                 |   |   |          |      |             | |
+ * |                                 |   |   |          |      | I/O Thread  | |
+ * |                                 |   |   |          |      |             | |
+ * |                                 |   |   |          ---------> [IOWork]  | |
+ * |                                 |  IPC  |                 |     |       | |
+ * |                                 |   |   |                 |     | (5)   | |
+ * |                                 |   |   |          --------------       | |
+ * |                                 |   |   |          |      |_____________| |
+ * |                                 |   |   |          |                      |
+ * |                                 |   |   |          V                      |
+ * |                                 |   |   |     [HandleResult]              |
+ * |                                 |   |   |          |                      |
+ * |                                 |       |          | (6)                  |
+ * |                                 |  (7)  |          V                      |
+ * |   [SetRequestResult]<---------------------[GetRequestResult]              |
+ * |       |                         |       |                                 |
+ * |       | (8)                     |   |   |                                 |
+ * |       V                         |   |   |                                 |
+ * |[HandlerCallback]                |  IPC  |                                 |
+ * |_______|_________________________|   |   |_________________________________|
+ *         |                             |
+ *         V
+ *        Page
+ *
+ * 1. From the process that is handling the request
+ * Child/Parent (it can be in any process):
+ *   (1) Call FileSystem API from content page with JS. Create a task and run.
+ *   The base constructor [FileSystemTaskChildBase()] of the task should be
+ *   called.
+ *   (2) Forward the task to the parent process through the IPC and call
+ *   [GetRequestParams] to prepare the parameters of the IPC.
+ * Parent:
+ *   (3) The parent process receives IPC and handle it in
+ *   FileystemRequestParent. Get the IPC parameters and create a task to run the
+ *   IPC task.
+ *   (4) The task operation will be performed in the member function of
+ * [IOWork]. A I/O  thread will be created to run that function. If error occurs
+ *   during the operation, call [SetError] to record the error and then abort.
+ *   (5) After finishing the task operation, call [HandleResult] to send the
+ *   result back to the child process though the IPC.
+ *   (6) Call [GetRequestResult] request result to prepare the parameters of the
+ *   IPC. Because the formats of the error result for different task are the
+ *   same, FileSystemTaskChildBase can handle the error message without
+ *   interfering.
+ *   Each task only needs to implement its specific success result preparation
+ *   function -[GetSuccessRequestResult].
+ * Child/Parent:
+ *   (7) The process receives IPC and calls [SetRequestResult] to get the
+ *   task result. Each task needs to implement its specific success result
+ *   parsing function [SetSuccessRequestResult] to get the success result.
+ *   (8) Call [HandlerCallback] to send the task result to the content page.
+ */
+class FileSystemTaskChildBase : public PFileSystemRequestChild {
+  friend class PFileSystemRequestChild;
+
+ public:
+  NS_INLINE_DECL_REFCOUNTING(FileSystemTaskChildBase, final)
+
+  /*
+   * Start the task. It will dispatch all the information to the parent process,
+   * PBackground thread. This method must be called from the owning thread.
+   */
+  void Start();
+
+  /*
+   * The error codes are defined in xpcom/base/ErrorList.h and their
+   * corresponding error name and message are defined in dom/base/domerr.msg.
+   */
+  void SetError(const nsresult& aErrorCode);
+
+  FileSystemBase* GetFileSystem() const;
+
+  /*
+   * After the task is completed, this function will be called to pass the task
+   * result to the content page. This method is called in the owning thread.
+   * Override this function to handle the call back to the content page.
+   */
+  virtual void HandlerCallback() = 0;
+
+  bool HasError() const { return NS_FAILED(mErrorValue); }
+
+ protected:
+  /*
+   * To create a task to handle the page content request.
+   */
+  FileSystemTaskChildBase(nsIGlobalObject* aGlobalObject,
+                          FileSystemBase* aFileSystem);
+
+  virtual ~FileSystemTaskChildBase();
+
+  /*
+   * Wrap the task parameter to FileSystemParams for sending it through IPC.
+   * It will be called when we need to forward a task from the child process to
+   * the parent process. This method runs in the owning thread.
+   * @param filesystem The string representation of the file system.
+   */
+  virtual FileSystemParams GetRequestParams(const nsString& aSerializedDOMPath,
+                                            ErrorResult& aRv) const = 0;
+
+  /*
+   * Unwrap the IPC message to get the task success result.
+   * It will be called when the task is completed successfully and an IPC
+   * message is received in the child process and we want to get the task
+   * success result. This method runs in the owning thread.
+   */
+  virtual void SetSuccessRequestResult(const FileSystemResponseValue& aValue,
+                                       ErrorResult& aRv) = 0;
+
+  // Overrides PFileSystemRequestChild
+  virtual mozilla::ipc::IPCResult Recv__delete__(
+      const FileSystemResponseValue& value) final;
+
+  nsresult mErrorValue;
+  RefPtr<FileSystemBase> mFileSystem;
+  nsCOMPtr<nsIGlobalObject> mGlobalObject;
+
+ private:
+  /*
+   * Unwrap the IPC message to get the task result.
+   * It will be called when the task is completed and an IPC message is received
+   * in the content process and we want to get the task result. This runs on the
+   * owning thread.
+   */
+  void SetRequestResult(const FileSystemResponseValue& aValue);
+};
+
+// This class is the 'alter ego' of FileSystemTaskChildBase in the PBackground
+// world.
+class FileSystemTaskParentBase : public Runnable {
+ public:
+  FileSystemTaskParentBase()
+      : Runnable("FileSystemTaskParentBase"),
+        mErrorValue(NS_ERROR_NOT_INITIALIZED) {}
+
+  /*
+   * Start the task. This must be called from the PBackground thread only.
+   */
+  void Start();
+
+  /*
+   * The error codes are defined in xpcom/base/ErrorList.h and their
+   * corresponding error name and message are defined in dom/base/domerr.msg.
+   */
+  void SetError(const nsresult& aErrorCode);
+
+  /*
+   * The function to perform task operation. It will be run on the I/O
+   * thread of the parent process.
+   * Overrides this function to define the task operation for individual task.
+   */
+  virtual nsresult IOWork() = 0;
+
+  /*
+   * Wrap the task success result to FileSystemResponseValue for sending it
+   * through IPC. This method runs in the PBackground thread.
+   * It will be called when the task is completed successfully and we need to
+   * send the task success result back to the child process.
+   */
+  virtual FileSystemResponseValue GetSuccessRequestResult(
+      ErrorResult& aRv) const = 0;
+
+  /*
+   * After finishing the task operation, handle the task result.
+   * If it is an IPC task, send back the IPC result. It runs on the PBackground
+   * thread.
+   */
+  void HandleResult();
+
+  bool HasError() const { return NS_FAILED(mErrorValue); }
+
+  NS_IMETHOD
+  Run() override;
+
+  virtual nsresult GetTargetPath(nsAString& aPath) const = 0;
+
+ private:
+  /*
+   * Wrap the task result to FileSystemResponseValue for sending it through IPC.
+   * It will be called when the task is completed and we need to
+   * send the task result back to the content. This runs on the PBackground
+   * thread.
+   */
+  FileSystemResponseValue GetRequestResult() const;
+
+ protected:
+  /*
+   * To create a parent process task delivered from the child process through
+   * IPC.
+   */
+  FileSystemTaskParentBase(FileSystemBase* aFileSystem,
+                           const FileSystemParams& aParam,
+                           FileSystemRequestParent* aParent);
+
+  virtual ~FileSystemTaskParentBase();
+
+  nsresult mErrorValue;
+  RefPtr<FileSystemBase> mFileSystem;
+  RefPtr<FileSystemRequestParent> mRequestParent;
+  nsCOMPtr<nsIEventTarget> mBackgroundEventTarget;
+};
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // mozilla_dom_FileSystemTaskBase_h
diff --git a/dom/filesystem/FileSystemUtils.cpp b/dom/filesystem/FileSystemUtils.cpp
new file mode 100644
index 0000000000..136f683e5e
--- /dev/null
+++ b/dom/filesystem/FileSystemUtils.cpp
@@ -0,0 +1,84 @@
+/* -*- 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/FileSystemUtils.h"
+#include "nsCharSeparatedTokenizer.h"
+#include "nsIEventTarget.h"
+#include "nsThreadUtils.h"
+
+namespace mozilla::dom {
+
+/* static */
+bool FileSystemUtils::IsDescendantPath(const nsAString& aPath,
+                                       const nsAString& aDescendantPath) {
+  // Check the sub-directory path to see if it has the parent path as prefix.
+  if (!aDescendantPath.Equals(aPath) &&
+      !StringBeginsWith(aDescendantPath, aPath)) {
+    return false;
+  }
+
+  return true;
+}
+
+/* static */
+bool FileSystemUtils::IsValidRelativeDOMPath(const nsAString& aPath,
+                                             nsTArray<nsString>& aParts) {
+  // We don't allow empty relative path to access the root.
+  if (aPath.IsEmpty()) {
+    return false;
+  }
+
+  // Leading and trailing "/" are not allowed.
+  if (aPath.First() == FILESYSTEM_DOM_PATH_SEPARATOR_CHAR ||
+      aPath.Last() == FILESYSTEM_DOM_PATH_SEPARATOR_CHAR) {
+    return false;
+  }
+
+  constexpr auto kCurrentDir = u"."_ns;
+  constexpr auto kParentDir = u".."_ns;
+
+  // Split path and check each path component.
+  for (const nsAString& pathComponent :
+       nsCharSeparatedTokenizerTemplate<NS_TokenizerIgnoreNothing>{
+           aPath, FILESYSTEM_DOM_PATH_SEPARATOR_CHAR}
+           .ToRange()) {
+    // The path containing empty components, such as "foo//bar", is invalid.
+    // We don't allow paths, such as "../foo", "foo/./bar" and "foo/../bar",
+    // to walk up the directory.
+    if (pathComponent.IsEmpty() || pathComponent.Equals(kCurrentDir) ||
+        pathComponent.Equals(kParentDir)) {
+      return false;
+    }
+
+    aParts.AppendElement(pathComponent);
+  }
+
+  return true;
+}
+
+/* static */
+nsresult FileSystemUtils::DispatchRunnable(
+    nsIGlobalObject* aGlobal, already_AddRefed<nsIRunnable>&& aRunnable) {
+  nsCOMPtr<nsIRunnable> runnable = aRunnable;
+
+  nsCOMPtr<nsIEventTarget> target;
+  if (!aGlobal) {
+    target = GetMainThreadSerialEventTarget();
+  } else {
+    target = aGlobal->SerialEventTarget();
+  }
+
+  MOZ_ASSERT(target);
+
+  nsresult rv = target->Dispatch(runnable.forget(), NS_DISPATCH_NORMAL);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/FileSystemUtils.h b/dom/filesystem/FileSystemUtils.h
new file mode 100644
index 0000000000..7f82e8474f
--- /dev/null
+++ b/dom/filesystem/FileSystemUtils.h
@@ -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/. */
+
+#ifndef mozilla_dom_FileSystemUtils_h
+#define mozilla_dom_FileSystemUtils_h
+
+#include "nsIGlobalObject.h"
+#include "nsStringFwd.h"
+#include "nsTArray.h"
+
+class nsIFile;
+class nsIRunnable;
+
+namespace mozilla::dom {
+
+#define FILESYSTEM_DOM_PATH_SEPARATOR_LITERAL "/"
+#define FILESYSTEM_DOM_PATH_SEPARATOR_CHAR '/'
+
+/*
+ * This class is for error handling.
+ * All methods in this class are static.
+ */
+class FileSystemUtils {
+ public:
+  /*
+   * Return true if aDescendantPath is a descendant of aPath.
+   */
+  static bool IsDescendantPath(const nsAString& aPath,
+                               const nsAString& aDescendantPath);
+
+  /**
+   * Return true if this is valid DOMPath. It also splits the path in
+   * subdirectories and stores them in aParts.
+   */
+  static bool IsValidRelativeDOMPath(const nsAString& aPath,
+                                     nsTArray<nsString>& aParts);
+
+  /**
+   * Helper method. If aGlobal is null, the SystemGroup EventTarget will be
+   * used.
+   */
+  static nsresult DispatchRunnable(nsIGlobalObject* aGlobal,
+                                   already_AddRefed<nsIRunnable>&& aRunnable);
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_FileSystemUtils_h
diff --git a/dom/filesystem/GetDirectoryListingTask.cpp b/dom/filesystem/GetDirectoryListingTask.cpp
new file mode 100644
index 0000000000..f78a04a9d0
--- /dev/null
+++ b/dom/filesystem/GetDirectoryListingTask.cpp
@@ -0,0 +1,371 @@
+/* -*- 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 "GetDirectoryListingTask.h"
+
+#include "HTMLSplitOnSpacesTokenizer.h"
+#include "js/Value.h"
+#include "mozilla/dom/FileBlobImpl.h"
+#include "mozilla/dom/FileSystemBase.h"
+#include "mozilla/dom/FileSystemUtils.h"
+#include "mozilla/dom/IPCBlobUtils.h"
+#include "mozilla/dom/PFileSystemParams.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/dom/UnionTypes.h"
+#include "mozilla/ipc/BackgroundParent.h"
+#include "nsIFile.h"
+#include "nsString.h"
+
+namespace mozilla::dom {
+
+/**
+ * GetDirectoryListingTaskChild
+ */
+
+/* static */
+already_AddRefed<GetDirectoryListingTaskChild>
+GetDirectoryListingTaskChild::Create(FileSystemBase* aFileSystem,
+                                     Directory* aDirectory,
+                                     nsIFile* aTargetPath,
+                                     const nsAString& aFilters,
+                                     ErrorResult& aRv) {
+  MOZ_ASSERT(aFileSystem);
+  MOZ_ASSERT(aDirectory);
+  aFileSystem->AssertIsOnOwningThread();
+
+  nsCOMPtr<nsIGlobalObject> globalObject = aFileSystem->GetParentObject();
+  MOZ_ASSERT(globalObject);
+
+  RefPtr<GetDirectoryListingTaskChild> task = new GetDirectoryListingTaskChild(
+      globalObject, aFileSystem, aDirectory, aTargetPath, aFilters);
+
+  // aTargetPath can be null. In this case SetError will be called.
+
+  task->mPromise = Promise::Create(globalObject, aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  return task.forget();
+}
+
+GetDirectoryListingTaskChild::GetDirectoryListingTaskChild(
+    nsIGlobalObject* aGlobalObject, FileSystemBase* aFileSystem,
+    Directory* aDirectory, nsIFile* aTargetPath, const nsAString& aFilters)
+    : FileSystemTaskChildBase(aGlobalObject, aFileSystem),
+      mDirectory(aDirectory),
+      mTargetPath(aTargetPath),
+      mFilters(aFilters) {
+  MOZ_ASSERT(aFileSystem);
+  aFileSystem->AssertIsOnOwningThread();
+}
+
+GetDirectoryListingTaskChild::~GetDirectoryListingTaskChild() {
+  mFileSystem->AssertIsOnOwningThread();
+}
+
+already_AddRefed<Promise> GetDirectoryListingTaskChild::GetPromise() {
+  mFileSystem->AssertIsOnOwningThread();
+  return RefPtr<Promise>(mPromise).forget();
+}
+
+FileSystemParams GetDirectoryListingTaskChild::GetRequestParams(
+    const nsString& aSerializedDOMPath, ErrorResult& aRv) const {
+  mFileSystem->AssertIsOnOwningThread();
+
+  // this is the real path.
+  nsAutoString path;
+  aRv = mTargetPath->GetPath(path);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return FileSystemGetDirectoryListingParams();
+  }
+
+  // this is the dom path.
+  nsAutoString directoryPath;
+  mDirectory->GetPath(directoryPath, aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return FileSystemGetDirectoryListingParams();
+  }
+
+  return FileSystemGetDirectoryListingParams(aSerializedDOMPath, path,
+                                             directoryPath, mFilters);
+}
+
+void GetDirectoryListingTaskChild::SetSuccessRequestResult(
+    const FileSystemResponseValue& aValue, ErrorResult& aRv) {
+  mFileSystem->AssertIsOnOwningThread();
+  MOZ_ASSERT(aValue.type() ==
+             FileSystemResponseValue::TFileSystemDirectoryListingResponse);
+
+  FileSystemDirectoryListingResponse r = aValue;
+  for (uint32_t i = 0; i < r.data().Length(); ++i) {
+    const FileSystemDirectoryListingResponseData& data = r.data()[i];
+
+    OwningFileOrDirectory* ofd = mTargetData.AppendElement(fallible);
+    if (!ofd) {
+      aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+      return;
+    }
+
+    if (data.type() == FileSystemDirectoryListingResponseData::
+                           TFileSystemDirectoryListingResponseFile) {
+      const FileSystemDirectoryListingResponseFile& d =
+          data.get_FileSystemDirectoryListingResponseFile();
+
+      RefPtr<BlobImpl> blobImpl = IPCBlobUtils::Deserialize(d.blob());
+      MOZ_ASSERT(blobImpl);
+
+      nsCOMPtr<nsIGlobalObject> globalObject = mFileSystem->GetParentObject();
+      MOZ_ASSERT(globalObject);
+
+      RefPtr<File> file = File::Create(globalObject, blobImpl);
+      MOZ_ASSERT(file);
+
+      ofd->SetAsFile() = file;
+    } else {
+      MOZ_ASSERT(data.type() ==
+                 FileSystemDirectoryListingResponseData::
+                     TFileSystemDirectoryListingResponseDirectory);
+      const FileSystemDirectoryListingResponseDirectory& d =
+          data.get_FileSystemDirectoryListingResponseDirectory();
+
+      nsCOMPtr<nsIFile> path;
+      aRv = NS_NewLocalFile(d.directoryRealPath(), true, getter_AddRefs(path));
+      if (NS_WARN_IF(aRv.Failed())) {
+        return;
+      }
+
+      RefPtr<Directory> directory =
+          Directory::Create(mFileSystem->GetParentObject(), path, mFileSystem);
+      MOZ_ASSERT(directory);
+
+      ofd->SetAsDirectory() = directory;
+    }
+  }
+}
+
+void GetDirectoryListingTaskChild::HandlerCallback() {
+  mFileSystem->AssertIsOnOwningThread();
+
+  if (mFileSystem->IsShutdown()) {
+    mPromise = nullptr;
+    return;
+  }
+
+  if (HasError()) {
+    mPromise->MaybeReject(mErrorValue);
+    mPromise = nullptr;
+    return;
+  }
+
+  mPromise->MaybeResolve(mTargetData);
+  mPromise = nullptr;
+}
+
+/**
+ * GetDirectoryListingTaskParent
+ */
+
+/* static */
+already_AddRefed<GetDirectoryListingTaskParent>
+GetDirectoryListingTaskParent::Create(
+    FileSystemBase* aFileSystem,
+    const FileSystemGetDirectoryListingParams& aParam,
+    FileSystemRequestParent* aParent, ErrorResult& aRv) {
+  MOZ_ASSERT(XRE_IsParentProcess(), "Only call from parent process!");
+  mozilla::ipc::AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aFileSystem);
+
+  RefPtr<GetDirectoryListingTaskParent> task =
+      new GetDirectoryListingTaskParent(aFileSystem, aParam, aParent);
+
+  aRv = NS_NewLocalFile(aParam.realPath(), true,
+                        getter_AddRefs(task->mTargetPath));
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  return task.forget();
+}
+
+GetDirectoryListingTaskParent::GetDirectoryListingTaskParent(
+    FileSystemBase* aFileSystem,
+    const FileSystemGetDirectoryListingParams& aParam,
+    FileSystemRequestParent* aParent)
+    : FileSystemTaskParentBase(aFileSystem, aParam, aParent),
+      mDOMPath(aParam.domPath()),
+      mFilters(aParam.filters()) {
+  MOZ_ASSERT(XRE_IsParentProcess(), "Only call from parent process!");
+  mozilla::ipc::AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aFileSystem);
+}
+
+FileSystemResponseValue GetDirectoryListingTaskParent::GetSuccessRequestResult(
+    ErrorResult& aRv) const {
+  mozilla::ipc::AssertIsOnBackgroundThread();
+
+  nsTArray<FileSystemDirectoryListingResponseData> inputs;
+
+  for (unsigned i = 0; i < mTargetData.Length(); i++) {
+    if (mTargetData[i].mType == FileOrDirectoryPath::eFilePath) {
+      nsCOMPtr<nsIFile> path;
+      nsresult rv =
+          NS_NewLocalFile(mTargetData[i].mPath, true, getter_AddRefs(path));
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        continue;
+      }
+
+      FileSystemDirectoryListingResponseFile fileData;
+      RefPtr<BlobImpl> blobImpl = new FileBlobImpl(path);
+
+      nsAutoString filePath;
+      filePath.Assign(mDOMPath);
+
+      // This is specific for unix root filesystem.
+      if (!mDOMPath.EqualsLiteral(FILESYSTEM_DOM_PATH_SEPARATOR_LITERAL)) {
+        filePath.AppendLiteral(FILESYSTEM_DOM_PATH_SEPARATOR_LITERAL);
+      }
+
+      nsAutoString name;
+      blobImpl->GetName(name);
+      filePath.Append(name);
+      blobImpl->SetDOMPath(filePath);
+
+      IPCBlob ipcBlob;
+      rv = IPCBlobUtils::Serialize(blobImpl, ipcBlob);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        continue;
+      }
+
+      fileData.blob() = ipcBlob;
+      inputs.AppendElement(fileData);
+    } else {
+      MOZ_ASSERT(mTargetData[i].mType == FileOrDirectoryPath::eDirectoryPath);
+      FileSystemDirectoryListingResponseDirectory directoryData;
+      directoryData.directoryRealPath() = mTargetData[i].mPath;
+      inputs.AppendElement(directoryData);
+    }
+  }
+
+  FileSystemDirectoryListingResponse response;
+  response.data() = std::move(inputs);
+  return response;
+}
+
+nsresult GetDirectoryListingTaskParent::IOWork() {
+  MOZ_ASSERT(XRE_IsParentProcess(), "Only call from parent process!");
+  MOZ_ASSERT(!NS_IsMainThread(), "Only call on worker thread!");
+
+  if (mFileSystem->IsShutdown()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  bool exists;
+  nsresult rv = mTargetPath->Exists(&exists);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  if (!exists) {
+    if (!mFileSystem->ShouldCreateDirectory()) {
+      return NS_ERROR_DOM_FILE_NOT_FOUND_ERR;
+    }
+
+    rv = mTargetPath->Create(nsIFile::DIRECTORY_TYPE, 0777);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+  }
+
+  // Get isDirectory.
+  bool isDir;
+  rv = mTargetPath->IsDirectory(&isDir);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  if (!isDir) {
+    return NS_ERROR_DOM_FILESYSTEM_TYPE_MISMATCH_ERR;
+  }
+
+  nsCOMPtr<nsIDirectoryEnumerator> entries;
+  rv = mTargetPath->GetDirectoryEntries(getter_AddRefs(entries));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  bool filterOutSensitive = false;
+  {
+    HTMLSplitOnSpacesTokenizer tokenizer(mFilters, ';');
+    nsAutoString token;
+    while (tokenizer.hasMoreTokens()) {
+      token = tokenizer.nextToken();
+      if (token.EqualsLiteral("filter-out-sensitive")) {
+        filterOutSensitive = true;
+      } else {
+        MOZ_CRASH("Unrecognized filter");
+      }
+    }
+  }
+
+  for (;;) {
+    nsCOMPtr<nsIFile> currFile;
+    if (NS_WARN_IF(NS_FAILED(entries->GetNextFile(getter_AddRefs(currFile)))) ||
+        !currFile) {
+      break;
+    }
+    bool isLink, isSpecial, isFile;
+    if (NS_WARN_IF(NS_FAILED(currFile->IsSymlink(&isLink)) ||
+                   NS_FAILED(currFile->IsSpecial(&isSpecial))) ||
+        // Although we allow explicit individual selection of symlinks via the
+        // file picker, we do not process symlinks in directory traversal.  Our
+        // specific policy decision is documented at
+        // https://bugzilla.mozilla.org/show_bug.cgi?id=1813299#c20
+        isLink || isSpecial) {
+      continue;
+    }
+    if (NS_WARN_IF(NS_FAILED(currFile->IsFile(&isFile)) ||
+                   NS_FAILED(currFile->IsDirectory(&isDir))) ||
+        !(isFile || isDir)) {
+      continue;
+    }
+
+    if (filterOutSensitive) {
+      bool isHidden;
+      if (NS_WARN_IF(NS_FAILED(currFile->IsHidden(&isHidden))) || isHidden) {
+        continue;
+      }
+      nsAutoString leafName;
+      if (NS_WARN_IF(NS_FAILED(currFile->GetLeafName(leafName)))) {
+        continue;
+      }
+      if (leafName[0] == char16_t('.')) {
+        continue;
+      }
+    }
+
+    nsAutoString path;
+    if (NS_WARN_IF(NS_FAILED(currFile->GetPath(path)))) {
+      continue;
+    }
+
+    FileOrDirectoryPath element;
+    element.mPath = path;
+    element.mType = isDir ? FileOrDirectoryPath::eDirectoryPath
+                          : FileOrDirectoryPath::eFilePath;
+
+    if (!mTargetData.AppendElement(element, fallible)) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+  }
+  return NS_OK;
+}
+
+nsresult GetDirectoryListingTaskParent::GetTargetPath(nsAString& aPath) const {
+  return mTargetPath->GetPath(aPath);
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/GetDirectoryListingTask.h b/dom/filesystem/GetDirectoryListingTask.h
new file mode 100644
index 0000000000..afb5296ac5
--- /dev/null
+++ b/dom/filesystem/GetDirectoryListingTask.h
@@ -0,0 +1,91 @@
+/* -*- 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_GetDirectoryListing_h
+#define mozilla_dom_GetDirectoryListing_h
+
+#include "mozilla/dom/Directory.h"
+#include "mozilla/dom/FileSystemTaskBase.h"
+
+namespace mozilla {
+class ErrorResult;
+
+namespace dom {
+
+class BlobImpl;
+class FileSystemGetDirectoryListingParams;
+class OwningFileOrDirectory;
+
+class GetDirectoryListingTaskChild final : public FileSystemTaskChildBase {
+ public:
+  static already_AddRefed<GetDirectoryListingTaskChild> Create(
+      FileSystemBase* aFileSystem, Directory* aDirectory, nsIFile* aTargetPath,
+      const nsAString& aFilters, ErrorResult& aRv);
+
+  virtual ~GetDirectoryListingTaskChild();
+
+  already_AddRefed<Promise> GetPromise();
+
+ private:
+  // If aDirectoryOnly is set, we should ensure that the target is a directory.
+  GetDirectoryListingTaskChild(nsIGlobalObject* aGlobalObject,
+                               FileSystemBase* aFileSystem,
+                               Directory* aDirectory, nsIFile* aTargetPath,
+                               const nsAString& aFilters);
+
+  virtual FileSystemParams GetRequestParams(const nsString& aSerializedDOMPath,
+                                            ErrorResult& aRv) const override;
+
+  virtual void SetSuccessRequestResult(const FileSystemResponseValue& aValue,
+                                       ErrorResult& aRv) override;
+
+  virtual void HandlerCallback() override;
+
+  RefPtr<Promise> mPromise;
+  RefPtr<Directory> mDirectory;
+  nsCOMPtr<nsIFile> mTargetPath;
+  nsString mFilters;
+
+  FallibleTArray<OwningFileOrDirectory> mTargetData;
+};
+
+class GetDirectoryListingTaskParent final : public FileSystemTaskParentBase {
+ public:
+  static already_AddRefed<GetDirectoryListingTaskParent> Create(
+      FileSystemBase* aFileSystem,
+      const FileSystemGetDirectoryListingParams& aParam,
+      FileSystemRequestParent* aParent, ErrorResult& aRv);
+
+  nsresult GetTargetPath(nsAString& aPath) const override;
+
+ private:
+  GetDirectoryListingTaskParent(
+      FileSystemBase* aFileSystem,
+      const FileSystemGetDirectoryListingParams& aParam,
+      FileSystemRequestParent* aParent);
+
+  virtual FileSystemResponseValue GetSuccessRequestResult(
+      ErrorResult& aRv) const override;
+
+  virtual nsresult IOWork() override;
+
+  nsCOMPtr<nsIFile> mTargetPath;
+  nsString mDOMPath;
+  nsString mFilters;
+
+  struct FileOrDirectoryPath {
+    nsString mPath;
+
+    enum { eFilePath, eDirectoryPath } mType;
+  };
+
+  FallibleTArray<FileOrDirectoryPath> mTargetData;
+};
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // mozilla_dom_GetDirectoryListing_h
diff --git a/dom/filesystem/GetFileOrDirectoryTask.cpp b/dom/filesystem/GetFileOrDirectoryTask.cpp
new file mode 100644
index 0000000000..7f7d1c2816
--- /dev/null
+++ b/dom/filesystem/GetFileOrDirectoryTask.cpp
@@ -0,0 +1,270 @@
+/* -*- 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 "GetFileOrDirectoryTask.h"
+
+#include "js/Value.h"
+#include "mozilla/dom/FileBlobImpl.h"
+#include "mozilla/dom/FileSystemBase.h"
+#include "mozilla/dom/FileSystemUtils.h"
+#include "mozilla/dom/PFileSystemParams.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/dom/IPCBlobUtils.h"
+#include "mozilla/ipc/BackgroundParent.h"
+#include "nsIFile.h"
+#include "nsString.h"
+
+namespace mozilla::dom {
+
+/**
+ * GetFileOrDirectoryTaskChild
+ */
+
+/* static */
+already_AddRefed<GetFileOrDirectoryTaskChild>
+GetFileOrDirectoryTaskChild::Create(FileSystemBase* aFileSystem,
+                                    nsIFile* aTargetPath, ErrorResult& aRv) {
+  MOZ_ASSERT(NS_IsMainThread(), "Only call on main thread!");
+  MOZ_ASSERT(aFileSystem);
+
+  nsCOMPtr<nsIGlobalObject> globalObject = aFileSystem->GetParentObject();
+  if (NS_WARN_IF(!globalObject)) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return nullptr;
+  }
+
+  RefPtr<GetFileOrDirectoryTaskChild> task =
+      new GetFileOrDirectoryTaskChild(globalObject, aFileSystem, aTargetPath);
+
+  // aTargetPath can be null. In this case SetError will be called.
+
+  task->mPromise = Promise::Create(globalObject, aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  return task.forget();
+}
+
+GetFileOrDirectoryTaskChild::GetFileOrDirectoryTaskChild(
+    nsIGlobalObject* aGlobalObject, FileSystemBase* aFileSystem,
+    nsIFile* aTargetPath)
+    : FileSystemTaskChildBase(aGlobalObject, aFileSystem),
+      mTargetPath(aTargetPath) {
+  MOZ_ASSERT(NS_IsMainThread(), "Only call on main thread!");
+  MOZ_ASSERT(aFileSystem);
+}
+
+GetFileOrDirectoryTaskChild::~GetFileOrDirectoryTaskChild() {
+  MOZ_ASSERT(NS_IsMainThread());
+}
+
+already_AddRefed<Promise> GetFileOrDirectoryTaskChild::GetPromise() {
+  MOZ_ASSERT(NS_IsMainThread(), "Only call on main thread!");
+  return RefPtr<Promise>(mPromise).forget();
+}
+
+FileSystemParams GetFileOrDirectoryTaskChild::GetRequestParams(
+    const nsString& aSerializedDOMPath, ErrorResult& aRv) const {
+  MOZ_ASSERT(NS_IsMainThread(), "Only call on main thread!");
+
+  nsAutoString path;
+  aRv = mTargetPath->GetPath(path);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return FileSystemGetFileOrDirectoryParams();
+  }
+
+  return FileSystemGetFileOrDirectoryParams(aSerializedDOMPath, path);
+}
+
+void GetFileOrDirectoryTaskChild::SetSuccessRequestResult(
+    const FileSystemResponseValue& aValue, ErrorResult& aRv) {
+  MOZ_ASSERT(NS_IsMainThread(), "Only call on main thread!");
+  switch (aValue.type()) {
+    case FileSystemResponseValue::TFileSystemFileResponse: {
+      FileSystemFileResponse r = aValue;
+
+      RefPtr<BlobImpl> blobImpl = IPCBlobUtils::Deserialize(r.blob());
+      MOZ_ASSERT(blobImpl);
+
+      nsCOMPtr<nsIGlobalObject> globalObject = mFileSystem->GetParentObject();
+      MOZ_ASSERT(globalObject);
+
+      mResultFile = File::Create(globalObject, blobImpl);
+      if (NS_WARN_IF(!mResultFile)) {
+        aRv.Throw(NS_ERROR_FAILURE);
+      }
+      break;
+    }
+    case FileSystemResponseValue::TFileSystemDirectoryResponse: {
+      FileSystemDirectoryResponse r = aValue;
+
+      nsCOMPtr<nsIFile> file;
+      aRv = NS_NewLocalFile(r.realPath(), true, getter_AddRefs(file));
+      if (NS_WARN_IF(aRv.Failed())) {
+        return;
+      }
+
+      mResultDirectory =
+          Directory::Create(mFileSystem->GetParentObject(), file, mFileSystem);
+      MOZ_ASSERT(mResultDirectory);
+      break;
+    }
+    default: {
+      MOZ_CRASH("not reached");
+      break;
+    }
+  }
+}
+
+void GetFileOrDirectoryTaskChild::HandlerCallback() {
+  MOZ_ASSERT(NS_IsMainThread(), "Only call on main thread!");
+  if (mFileSystem->IsShutdown()) {
+    mPromise = nullptr;
+    return;
+  }
+
+  if (HasError()) {
+    mPromise->MaybeReject(mErrorValue);
+    mPromise = nullptr;
+    return;
+  }
+
+  if (mResultDirectory) {
+    mPromise->MaybeResolve(mResultDirectory);
+    mResultDirectory = nullptr;
+    mPromise = nullptr;
+    return;
+  }
+
+  MOZ_ASSERT(mResultFile);
+  mPromise->MaybeResolve(mResultFile);
+  mResultFile = nullptr;
+  mPromise = nullptr;
+}
+
+/**
+ * GetFileOrDirectoryTaskParent
+ */
+
+/* static */
+already_AddRefed<GetFileOrDirectoryTaskParent>
+GetFileOrDirectoryTaskParent::Create(
+    FileSystemBase* aFileSystem,
+    const FileSystemGetFileOrDirectoryParams& aParam,
+    FileSystemRequestParent* aParent, ErrorResult& aRv) {
+  MOZ_ASSERT(XRE_IsParentProcess(), "Only call from parent process!");
+  mozilla::ipc::AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aFileSystem);
+
+  RefPtr<GetFileOrDirectoryTaskParent> task =
+      new GetFileOrDirectoryTaskParent(aFileSystem, aParam, aParent);
+
+  aRv = NS_NewLocalFile(aParam.realPath(), true,
+                        getter_AddRefs(task->mTargetPath));
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  return task.forget();
+}
+
+GetFileOrDirectoryTaskParent::GetFileOrDirectoryTaskParent(
+    FileSystemBase* aFileSystem,
+    const FileSystemGetFileOrDirectoryParams& aParam,
+    FileSystemRequestParent* aParent)
+    : FileSystemTaskParentBase(aFileSystem, aParam, aParent),
+      mIsDirectory(false) {
+  MOZ_ASSERT(XRE_IsParentProcess(), "Only call from parent process!");
+  mozilla::ipc::AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aFileSystem);
+}
+
+FileSystemResponseValue GetFileOrDirectoryTaskParent::GetSuccessRequestResult(
+    ErrorResult& aRv) const {
+  mozilla::ipc::AssertIsOnBackgroundThread();
+
+  nsAutoString path;
+  aRv = mTargetPath->GetPath(path);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return FileSystemDirectoryResponse();
+  }
+
+  if (mIsDirectory) {
+    return FileSystemDirectoryResponse(path);
+  }
+
+  RefPtr<BlobImpl> blobImpl = new FileBlobImpl(mTargetPath);
+
+  IPCBlob ipcBlob;
+  aRv = IPCBlobUtils::Serialize(blobImpl, ipcBlob);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return FileSystemDirectoryResponse();
+  }
+
+  return FileSystemFileResponse(ipcBlob);
+}
+
+nsresult GetFileOrDirectoryTaskParent::IOWork() {
+  MOZ_ASSERT(XRE_IsParentProcess(), "Only call from parent process!");
+  MOZ_ASSERT(!NS_IsMainThread(), "Only call on worker thread!");
+
+  if (mFileSystem->IsShutdown()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Whether we want to get the root directory.
+  bool exists;
+  nsresult rv = mTargetPath->Exists(&exists);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  if (!exists) {
+    if (!mFileSystem->ShouldCreateDirectory()) {
+      return NS_ERROR_DOM_FILE_NOT_FOUND_ERR;
+    }
+
+    rv = mTargetPath->Create(nsIFile::DIRECTORY_TYPE, 0777);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+  }
+
+  // Get isDirectory.
+  rv = mTargetPath->IsDirectory(&mIsDirectory);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  if (mIsDirectory) {
+    return NS_OK;
+  }
+
+  bool isFile;
+  // Get isFile
+  rv = mTargetPath->IsFile(&isFile);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  if (!isFile) {
+    // Neither directory or file.
+    return NS_ERROR_DOM_FILESYSTEM_TYPE_MISMATCH_ERR;
+  }
+
+  if (!mFileSystem->IsSafeFile(mTargetPath)) {
+    return NS_ERROR_DOM_SECURITY_ERR;
+  }
+
+  return NS_OK;
+}
+
+nsresult GetFileOrDirectoryTaskParent::GetTargetPath(nsAString& aPath) const {
+  return mTargetPath->GetPath(aPath);
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/GetFileOrDirectoryTask.h b/dom/filesystem/GetFileOrDirectoryTask.h
new file mode 100644
index 0000000000..8d15d9804f
--- /dev/null
+++ b/dom/filesystem/GetFileOrDirectoryTask.h
@@ -0,0 +1,79 @@
+/* -*- 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_GetFileOrDirectory_h
+#define mozilla_dom_GetFileOrDirectory_h
+
+#include "mozilla/dom/Directory.h"
+#include "mozilla/dom/FileSystemTaskBase.h"
+
+namespace mozilla {
+class ErrorResult;
+
+namespace dom {
+
+class BlobImpl;
+class FileSystemGetFileOrDirectoryParams;
+
+class GetFileOrDirectoryTaskChild final : public FileSystemTaskChildBase {
+ public:
+  static already_AddRefed<GetFileOrDirectoryTaskChild> Create(
+      FileSystemBase* aFileSystem, nsIFile* aTargetPath, ErrorResult& aRv);
+
+  virtual ~GetFileOrDirectoryTaskChild();
+
+  already_AddRefed<Promise> GetPromise();
+
+ protected:
+  virtual FileSystemParams GetRequestParams(const nsString& aSerializedDOMPath,
+                                            ErrorResult& aRv) const override;
+
+  virtual void SetSuccessRequestResult(const FileSystemResponseValue& aValue,
+                                       ErrorResult& aRv) override;
+  virtual void HandlerCallback() override;
+
+ private:
+  GetFileOrDirectoryTaskChild(nsIGlobalObject* aGlobalObject,
+                              FileSystemBase* aFileSystem,
+                              nsIFile* aTargetPath);
+
+  RefPtr<Promise> mPromise;
+  nsCOMPtr<nsIFile> mTargetPath;
+
+  RefPtr<File> mResultFile;
+  RefPtr<Directory> mResultDirectory;
+};
+
+class GetFileOrDirectoryTaskParent final : public FileSystemTaskParentBase {
+ public:
+  static already_AddRefed<GetFileOrDirectoryTaskParent> Create(
+      FileSystemBase* aFileSystem,
+      const FileSystemGetFileOrDirectoryParams& aParam,
+      FileSystemRequestParent* aParent, ErrorResult& aRv);
+
+  nsresult GetTargetPath(nsAString& aPath) const override;
+
+ protected:
+  virtual FileSystemResponseValue GetSuccessRequestResult(
+      ErrorResult& aRv) const override;
+
+  virtual nsresult IOWork() override;
+
+ private:
+  GetFileOrDirectoryTaskParent(FileSystemBase* aFileSystem,
+                               const FileSystemGetFileOrDirectoryParams& aParam,
+                               FileSystemRequestParent* aParent);
+
+  nsCOMPtr<nsIFile> mTargetPath;
+
+  // Whether we get a directory.
+  bool mIsDirectory;
+};
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // mozilla_dom_GetFileOrDirectory_h
diff --git a/dom/filesystem/GetFilesHelper.cpp b/dom/filesystem/GetFilesHelper.cpp
new file mode 100644
index 0000000000..5c91b4cfe5
--- /dev/null
+++ b/dom/filesystem/GetFilesHelper.cpp
@@ -0,0 +1,506 @@
+/* -*- 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 "GetFilesHelper.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/Directory.h"
+#include "mozilla/dom/FileBlobImpl.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/dom/UnionTypes.h"
+#include "mozilla/dom/IPCBlobUtils.h"
+#include "mozilla/ipc/IPCStreamUtils.h"
+#include "FileSystemUtils.h"
+#include "nsNetCID.h"
+#include "nsProxyRelease.h"
+
+namespace mozilla::dom {
+
+namespace {
+
+// This class is used in the DTOR of GetFilesHelper to release resources in the
+// correct thread.
+class ReleaseRunnable final : public Runnable {
+ public:
+  static void MaybeReleaseOnMainThread(
+      nsTArray<RefPtr<Promise>>&& aPromises,
+      nsTArray<RefPtr<GetFilesCallback>>&& aCallbacks) {
+    if (NS_IsMainThread()) {
+      return;
+    }
+
+    RefPtr<ReleaseRunnable> runnable =
+        new ReleaseRunnable(std::move(aPromises), std::move(aCallbacks));
+    FileSystemUtils::DispatchRunnable(nullptr, runnable.forget());
+  }
+
+  NS_IMETHOD
+  Run() override {
+    MOZ_ASSERT(NS_IsMainThread());
+
+    mPromises.Clear();
+    mCallbacks.Clear();
+
+    return NS_OK;
+  }
+
+ private:
+  ReleaseRunnable(nsTArray<RefPtr<Promise>>&& aPromises,
+                  nsTArray<RefPtr<GetFilesCallback>>&& aCallbacks)
+      : Runnable("dom::ReleaseRunnable"),
+        mPromises(std::move(aPromises)),
+        mCallbacks(std::move(aCallbacks)) {}
+
+  nsTArray<RefPtr<Promise>> mPromises;
+  nsTArray<RefPtr<GetFilesCallback>> mCallbacks;
+};
+
+}  // namespace
+
+///////////////////////////////////////////////////////////////////////////////
+// GetFilesHelper Base class
+
+already_AddRefed<GetFilesHelper> GetFilesHelper::Create(
+    const nsTArray<OwningFileOrDirectory>& aFilesOrDirectory,
+    bool aRecursiveFlag, ErrorResult& aRv) {
+  RefPtr<GetFilesHelper> helper;
+
+  if (XRE_IsParentProcess()) {
+    helper = new GetFilesHelper(aRecursiveFlag);
+  } else {
+    helper = new GetFilesHelperChild(aRecursiveFlag);
+  }
+
+  nsAutoString directoryPath;
+
+  for (uint32_t i = 0; i < aFilesOrDirectory.Length(); ++i) {
+    const OwningFileOrDirectory& data = aFilesOrDirectory[i];
+    if (data.IsFile()) {
+      if (!helper->mTargetBlobImplArray.AppendElement(data.GetAsFile()->Impl(),
+                                                      fallible)) {
+        aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+        return nullptr;
+      }
+    } else {
+      MOZ_ASSERT(data.IsDirectory());
+
+      // We support the upload of only 1 top-level directory from our
+      // directory picker. This means that we cannot have more than 1
+      // Directory object in aFilesOrDirectory array.
+      MOZ_ASSERT(directoryPath.IsEmpty());
+
+      RefPtr<Directory> directory = data.GetAsDirectory();
+      MOZ_ASSERT(directory);
+
+      aRv = directory->GetFullRealPath(directoryPath);
+      if (NS_WARN_IF(aRv.Failed())) {
+        return nullptr;
+      }
+    }
+  }
+
+  // No directories to explore.
+  if (directoryPath.IsEmpty()) {
+    helper->mListingCompleted = true;
+    return helper.forget();
+  }
+
+  MOZ_ASSERT(helper->mTargetBlobImplArray.IsEmpty());
+  helper->SetDirectoryPath(directoryPath);
+
+  helper->Work(aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  return helper.forget();
+}
+
+GetFilesHelper::GetFilesHelper(bool aRecursiveFlag)
+    : Runnable("GetFilesHelper"),
+      GetFilesHelperBase(aRecursiveFlag),
+      mListingCompleted(false),
+      mErrorResult(NS_OK),
+      mMutex("GetFilesHelper::mMutex"),
+      mCanceled(false) {}
+
+GetFilesHelper::~GetFilesHelper() {
+  ReleaseRunnable::MaybeReleaseOnMainThread(std::move(mPromises),
+                                            std::move(mCallbacks));
+}
+
+void GetFilesHelper::AddPromise(Promise* aPromise) {
+  MOZ_ASSERT(aPromise);
+
+  // Still working.
+  if (!mListingCompleted) {
+    mPromises.AppendElement(aPromise);
+    return;
+  }
+
+  MOZ_ASSERT(mPromises.IsEmpty());
+  ResolveOrRejectPromise(aPromise);
+}
+
+void GetFilesHelper::AddCallback(GetFilesCallback* aCallback) {
+  MOZ_ASSERT(aCallback);
+
+  // Still working.
+  if (!mListingCompleted) {
+    mCallbacks.AppendElement(aCallback);
+    return;
+  }
+
+  MOZ_ASSERT(mCallbacks.IsEmpty());
+  RunCallback(aCallback);
+}
+
+void GetFilesHelper::Unlink() {
+  mPromises.Clear();
+  mCallbacks.Clear();
+
+  {
+    MutexAutoLock lock(mMutex);
+    mCanceled = true;
+  }
+
+  Cancel();
+}
+
+void GetFilesHelper::Traverse(nsCycleCollectionTraversalCallback& cb) {
+  GetFilesHelper* tmp = this;
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mPromises);
+}
+
+void GetFilesHelper::Work(ErrorResult& aRv) {
+  nsCOMPtr<nsIEventTarget> target =
+      do_GetService(NS_STREAMTRANSPORTSERVICE_CONTRACTID);
+  MOZ_ASSERT(target);
+
+  aRv = target->Dispatch(this, NS_DISPATCH_NORMAL);
+}
+
+NS_IMETHODIMP
+GetFilesHelper::Run() {
+  MOZ_ASSERT(!mDirectoryPath.IsEmpty());
+  MOZ_ASSERT(!mListingCompleted);
+
+  // First step is to retrieve the list of file paths.
+  // This happens in the I/O thread.
+  if (!NS_IsMainThread()) {
+    RunIO();
+
+    // If this operation has been canceled, we don't have to go back to
+    // main-thread.
+    if (IsCanceled()) {
+      return NS_OK;
+    }
+
+    RefPtr<Runnable> runnable = this;
+    return FileSystemUtils::DispatchRunnable(nullptr, runnable.forget());
+  }
+
+  // We are here, but we should not do anything on this thread because, in the
+  // meantime, the operation has been canceled.
+  if (IsCanceled()) {
+    return NS_OK;
+  }
+
+  OperationCompleted();
+  return NS_OK;
+}
+
+void GetFilesHelper::OperationCompleted() {
+  // We mark the operation as completed here.
+  mListingCompleted = true;
+
+  // Let's process the pending promises.
+  nsTArray<RefPtr<Promise>> promises = std::move(mPromises);
+
+  for (uint32_t i = 0; i < promises.Length(); ++i) {
+    ResolveOrRejectPromise(promises[i]);
+  }
+
+  // Let's process the pending callbacks.
+  nsTArray<RefPtr<GetFilesCallback>> callbacks = std::move(mCallbacks);
+
+  for (uint32_t i = 0; i < callbacks.Length(); ++i) {
+    RunCallback(callbacks[i]);
+  }
+}
+
+void GetFilesHelper::RunIO() {
+  MOZ_ASSERT(!NS_IsMainThread());
+  MOZ_ASSERT(!mDirectoryPath.IsEmpty());
+  MOZ_ASSERT(!mListingCompleted);
+
+  nsCOMPtr<nsIFile> file;
+  mErrorResult = NS_NewLocalFile(mDirectoryPath, true, getter_AddRefs(file));
+  if (NS_WARN_IF(NS_FAILED(mErrorResult))) {
+    return;
+  }
+
+  nsAutoString leafName;
+  mErrorResult = file->GetLeafName(leafName);
+  if (NS_WARN_IF(NS_FAILED(mErrorResult))) {
+    return;
+  }
+
+  nsAutoString domPath;
+  domPath.AssignLiteral(FILESYSTEM_DOM_PATH_SEPARATOR_LITERAL);
+  domPath.Append(leafName);
+
+  mErrorResult = ExploreDirectory(domPath, file);
+}
+
+nsresult GetFilesHelperBase::ExploreDirectory(const nsAString& aDOMPath,
+                                              nsIFile* aFile) {
+  MOZ_ASSERT(!NS_IsMainThread());
+  MOZ_ASSERT(aFile);
+
+  // We check if this operation has to be terminated at each recursion.
+  if (IsCanceled()) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIDirectoryEnumerator> entries;
+  nsresult rv = aFile->GetDirectoryEntries(getter_AddRefs(entries));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  for (;;) {
+    nsCOMPtr<nsIFile> currFile;
+    if (NS_WARN_IF(NS_FAILED(entries->GetNextFile(getter_AddRefs(currFile)))) ||
+        !currFile) {
+      break;
+    }
+    bool isLink, isSpecial, isFile, isDir;
+    if (NS_WARN_IF(NS_FAILED(currFile->IsSymlink(&isLink)) ||
+                   NS_FAILED(currFile->IsSpecial(&isSpecial))) ||
+        isSpecial ||
+        // Although we allow explicit individual selection of symlinks via the
+        // file picker, we do not process symlinks in directory traversal.  Our
+        // specific policy decision is documented at
+        // https://bugzilla.mozilla.org/show_bug.cgi?id=1813299#c20
+        isLink) {
+      continue;
+    }
+
+    if (NS_WARN_IF(NS_FAILED(currFile->IsFile(&isFile)) ||
+                   NS_FAILED(currFile->IsDirectory(&isDir))) ||
+        !(isFile || isDir)) {
+      continue;
+    }
+
+    // The new domPath
+    nsAutoString domPath;
+    domPath.Assign(aDOMPath);
+    if (!aDOMPath.EqualsLiteral(FILESYSTEM_DOM_PATH_SEPARATOR_LITERAL)) {
+      domPath.AppendLiteral(FILESYSTEM_DOM_PATH_SEPARATOR_LITERAL);
+    }
+
+    nsAutoString leafName;
+    if (NS_WARN_IF(NS_FAILED(currFile->GetLeafName(leafName)))) {
+      continue;
+    }
+    domPath.Append(leafName);
+
+    if (isFile) {
+      RefPtr<BlobImpl> blobImpl = new FileBlobImpl(currFile);
+      blobImpl->SetDOMPath(domPath);
+
+      if (!mTargetBlobImplArray.AppendElement(blobImpl, fallible)) {
+        return NS_ERROR_OUT_OF_MEMORY;
+      }
+
+      continue;
+    }
+
+    MOZ_ASSERT(isDir);
+    if (!mRecursiveFlag) {
+      continue;
+    }
+
+    // Recursive.
+    rv = ExploreDirectory(domPath, currFile);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+  }
+
+  return NS_OK;
+}
+
+void GetFilesHelper::ResolveOrRejectPromise(Promise* aPromise) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(mListingCompleted);
+  MOZ_ASSERT(aPromise);
+
+  Sequence<RefPtr<File>> files;
+
+  if (NS_SUCCEEDED(mErrorResult)) {
+    for (uint32_t i = 0; i < mTargetBlobImplArray.Length(); ++i) {
+      RefPtr<File> domFile =
+          File::Create(aPromise->GetParentObject(), mTargetBlobImplArray[i]);
+      if (NS_WARN_IF(!domFile)) {
+        mErrorResult = NS_ERROR_FAILURE;
+        files.Clear();
+        break;
+      }
+
+      if (!files.AppendElement(domFile, fallible)) {
+        mErrorResult = NS_ERROR_OUT_OF_MEMORY;
+        files.Clear();
+        break;
+      }
+    }
+  }
+
+  // Error propagation.
+  if (NS_FAILED(mErrorResult)) {
+    aPromise->MaybeReject(mErrorResult);
+    return;
+  }
+
+  aPromise->MaybeResolve(files);
+}
+
+void GetFilesHelper::RunCallback(GetFilesCallback* aCallback) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(mListingCompleted);
+  MOZ_ASSERT(aCallback);
+
+  aCallback->Callback(mErrorResult, mTargetBlobImplArray);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// GetFilesHelperChild class
+
+void GetFilesHelperChild::Work(ErrorResult& aRv) {
+  ContentChild* cc = ContentChild::GetSingleton();
+  if (NS_WARN_IF(!cc)) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return;
+  }
+
+  aRv = nsID::GenerateUUIDInPlace(mUUID);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  mPendingOperation = true;
+  cc->CreateGetFilesRequest(mDirectoryPath, mRecursiveFlag, mUUID, this);
+}
+
+void GetFilesHelperChild::Cancel() {
+  if (!mPendingOperation) {
+    return;
+  }
+
+  ContentChild* cc = ContentChild::GetSingleton();
+  if (NS_WARN_IF(!cc)) {
+    return;
+  }
+
+  mPendingOperation = false;
+  cc->DeleteGetFilesRequest(mUUID, this);
+}
+
+bool GetFilesHelperChild::AppendBlobImpl(BlobImpl* aBlobImpl) {
+  MOZ_ASSERT(mPendingOperation);
+  MOZ_ASSERT(aBlobImpl);
+  MOZ_ASSERT(aBlobImpl->IsFile());
+
+  return mTargetBlobImplArray.AppendElement(aBlobImpl, fallible);
+}
+
+void GetFilesHelperChild::Finished(nsresult aError) {
+  MOZ_ASSERT(mPendingOperation);
+  MOZ_ASSERT(NS_SUCCEEDED(mErrorResult));
+
+  mPendingOperation = false;
+  mErrorResult = aError;
+
+  OperationCompleted();
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// GetFilesHelperParent class
+
+class GetFilesHelperParentCallback final : public GetFilesCallback {
+ public:
+  explicit GetFilesHelperParentCallback(GetFilesHelperParent* aParent)
+      : mParent(aParent) {
+    MOZ_ASSERT(aParent);
+  }
+
+  void Callback(nsresult aStatus,
+                const FallibleTArray<RefPtr<BlobImpl>>& aBlobImpls) override {
+    if (NS_FAILED(aStatus)) {
+      mParent->mContentParent->SendGetFilesResponseAndForget(
+          mParent->mUUID, GetFilesResponseFailure(aStatus));
+      return;
+    }
+
+    GetFilesResponseSuccess success;
+
+    nsTArray<IPCBlob>& ipcBlobs = success.blobs();
+    ipcBlobs.SetLength(aBlobImpls.Length());
+
+    for (uint32_t i = 0; i < aBlobImpls.Length(); ++i) {
+      nsresult rv = IPCBlobUtils::Serialize(aBlobImpls[i], ipcBlobs[i]);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        mParent->mContentParent->SendGetFilesResponseAndForget(
+            mParent->mUUID, GetFilesResponseFailure(NS_ERROR_OUT_OF_MEMORY));
+        return;
+      }
+    }
+
+    mParent->mContentParent->SendGetFilesResponseAndForget(mParent->mUUID,
+                                                           success);
+  }
+
+ private:
+  // Raw pointer because this callback is kept alive by this parent object.
+  GetFilesHelperParent* mParent;
+};
+
+GetFilesHelperParent::GetFilesHelperParent(const nsID& aUUID,
+                                           ContentParent* aContentParent,
+                                           bool aRecursiveFlag)
+    : GetFilesHelper(aRecursiveFlag),
+      mContentParent(aContentParent),
+      mUUID(aUUID) {}
+
+GetFilesHelperParent::~GetFilesHelperParent() {
+  NS_ReleaseOnMainThread("GetFilesHelperParent::mContentParent",
+                         mContentParent.forget());
+}
+
+/* static */
+already_AddRefed<GetFilesHelperParent> GetFilesHelperParent::Create(
+    const nsID& aUUID, const nsAString& aDirectoryPath, bool aRecursiveFlag,
+    ContentParent* aContentParent, ErrorResult& aRv) {
+  MOZ_ASSERT(aContentParent);
+
+  RefPtr<GetFilesHelperParent> helper =
+      new GetFilesHelperParent(aUUID, aContentParent, aRecursiveFlag);
+  helper->SetDirectoryPath(aDirectoryPath);
+
+  helper->Work(aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  RefPtr<GetFilesHelperParentCallback> callback =
+      new GetFilesHelperParentCallback(helper);
+  helper->AddCallback(callback);
+
+  return helper.forget();
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/GetFilesHelper.h b/dom/filesystem/GetFilesHelper.h
new file mode 100644
index 0000000000..2b15e69059
--- /dev/null
+++ b/dom/filesystem/GetFilesHelper.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_GetFilesHelper_h
+#define mozilla_dom_GetFilesHelper_h
+
+#include "mozilla/Mutex.h"
+#include "mozilla/RefPtr.h"
+#include "nsCycleCollectionTraversalCallback.h"
+#include "nsTArray.h"
+#include "nsThreadUtils.h"
+
+class nsIGlobalObject;
+
+namespace mozilla {
+class ErrorResult;
+
+namespace dom {
+
+class BlobImpl;
+class ContentParent;
+class File;
+class GetFilesHelperParent;
+class OwningFileOrDirectory;
+class Promise;
+
+class GetFilesCallback {
+ public:
+  NS_INLINE_DECL_REFCOUNTING(GetFilesCallback);
+
+  virtual void Callback(nsresult aStatus,
+                        const FallibleTArray<RefPtr<BlobImpl>>& aBlobImpls) = 0;
+
+ protected:
+  virtual ~GetFilesCallback() = default;
+};
+
+class GetFilesHelperBase {
+ protected:
+  explicit GetFilesHelperBase(bool aRecursiveFlag)
+      : mRecursiveFlag(aRecursiveFlag) {}
+
+  virtual ~GetFilesHelperBase() = default;
+
+  virtual bool IsCanceled() { return false; }
+
+  nsresult ExploreDirectory(const nsAString& aDOMPath, nsIFile* aFile);
+
+  bool mRecursiveFlag;
+
+  // We populate this array in the I/O thread with the BlobImpl.
+  FallibleTArray<RefPtr<BlobImpl>> mTargetBlobImplArray;
+};
+
+// Retrieving the list of files can be very time/IO consuming. We use this
+// helper class to do it just once.
+class GetFilesHelper : public Runnable, public GetFilesHelperBase {
+  friend class GetFilesHelperParent;
+
+ public:
+  static already_AddRefed<GetFilesHelper> Create(
+      const nsTArray<OwningFileOrDirectory>& aFilesOrDirectory,
+      bool aRecursiveFlag, ErrorResult& aRv);
+
+  void AddPromise(Promise* aPromise);
+
+  void AddCallback(GetFilesCallback* aCallback);
+
+  // CC methods
+  void Unlink();
+  void Traverse(nsCycleCollectionTraversalCallback& cb);
+
+ protected:
+  explicit GetFilesHelper(bool aRecursiveFlag);
+
+  virtual ~GetFilesHelper();
+
+  void SetDirectoryPath(const nsAString& aDirectoryPath) {
+    mDirectoryPath = aDirectoryPath;
+  }
+
+  virtual bool IsCanceled() override {
+    MutexAutoLock lock(mMutex);
+    return mCanceled;
+  }
+
+  virtual void Work(ErrorResult& aRv);
+
+  virtual void Cancel(){};
+
+  NS_IMETHOD
+  Run() override;
+
+  void RunIO();
+
+  void OperationCompleted();
+
+  void ResolveOrRejectPromise(Promise* aPromise);
+
+  void RunCallback(GetFilesCallback* aCallback);
+
+  bool mListingCompleted;
+  nsString mDirectoryPath;
+
+  // Error code to propagate.
+  nsresult mErrorResult;
+
+  nsTArray<RefPtr<Promise>> mPromises;
+  nsTArray<RefPtr<GetFilesCallback>> mCallbacks;
+
+  Mutex mMutex MOZ_UNANNOTATED;
+
+  // This variable is protected by mutex.
+  bool mCanceled;
+};
+
+class GetFilesHelperChild final : public GetFilesHelper {
+ public:
+  explicit GetFilesHelperChild(bool aRecursiveFlag)
+      : GetFilesHelper(aRecursiveFlag), mPendingOperation(false) {}
+
+  virtual void Work(ErrorResult& aRv) override;
+
+  virtual void Cancel() override;
+
+  bool AppendBlobImpl(BlobImpl* aBlobImpl);
+
+  void Finished(nsresult aResult);
+
+ private:
+  nsID mUUID;
+  bool mPendingOperation;
+};
+
+class GetFilesHelperParentCallback;
+
+class GetFilesHelperParent final : public GetFilesHelper {
+  friend class GetFilesHelperParentCallback;
+
+ public:
+  static already_AddRefed<GetFilesHelperParent> Create(
+      const nsID& aUUID, const nsAString& aDirectoryPath, bool aRecursiveFlag,
+      ContentParent* aContentParent, ErrorResult& aRv);
+
+ private:
+  GetFilesHelperParent(const nsID& aUUID, ContentParent* aContentParent,
+                       bool aRecursiveFlag);
+
+  ~GetFilesHelperParent();
+
+  RefPtr<ContentParent> mContentParent;
+  nsID mUUID;
+};
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // mozilla_dom_GetFilesHelper_h
diff --git a/dom/filesystem/GetFilesTask.cpp b/dom/filesystem/GetFilesTask.cpp
new file mode 100644
index 0000000000..280df0b0bc
--- /dev/null
+++ b/dom/filesystem/GetFilesTask.cpp
@@ -0,0 +1,246 @@
+/* -*- 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 "GetFilesTask.h"
+
+#include "HTMLSplitOnSpacesTokenizer.h"
+#include "js/Value.h"
+#include "mozilla/dom/BlobImpl.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/dom/FileSystemBase.h"
+#include "mozilla/dom/FileSystemUtils.h"
+#include "mozilla/dom/IPCBlobUtils.h"
+#include "mozilla/dom/PFileSystemParams.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/ipc/BackgroundParent.h"
+#include "nsIFile.h"
+#include "nsString.h"
+
+namespace mozilla::dom {
+
+/**
+ * GetFilesTaskChild
+ */
+
+/* static */
+already_AddRefed<GetFilesTaskChild> GetFilesTaskChild::Create(
+    FileSystemBase* aFileSystem, Directory* aDirectory, nsIFile* aTargetPath,
+    bool aRecursiveFlag, ErrorResult& aRv) {
+  MOZ_ASSERT(aFileSystem);
+  MOZ_ASSERT(aDirectory);
+  aFileSystem->AssertIsOnOwningThread();
+
+  nsCOMPtr<nsIGlobalObject> globalObject = aFileSystem->GetParentObject();
+  if (NS_WARN_IF(!globalObject)) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return nullptr;
+  }
+
+  RefPtr<GetFilesTaskChild> task = new GetFilesTaskChild(
+      globalObject, aFileSystem, aDirectory, aTargetPath, aRecursiveFlag);
+
+  // aTargetPath can be null. In this case SetError will be called.
+
+  task->mPromise = Promise::Create(globalObject, aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  return task.forget();
+}
+
+GetFilesTaskChild::GetFilesTaskChild(nsIGlobalObject* aGlobalObject,
+                                     FileSystemBase* aFileSystem,
+                                     Directory* aDirectory,
+                                     nsIFile* aTargetPath, bool aRecursiveFlag)
+    : FileSystemTaskChildBase(aGlobalObject, aFileSystem),
+      mDirectory(aDirectory),
+      mTargetPath(aTargetPath),
+      mRecursiveFlag(aRecursiveFlag) {
+  MOZ_ASSERT(aFileSystem);
+  MOZ_ASSERT(aDirectory);
+  aFileSystem->AssertIsOnOwningThread();
+}
+
+GetFilesTaskChild::~GetFilesTaskChild() {
+  mFileSystem->AssertIsOnOwningThread();
+}
+
+already_AddRefed<Promise> GetFilesTaskChild::GetPromise() {
+  mFileSystem->AssertIsOnOwningThread();
+  return RefPtr<Promise>(mPromise).forget();
+}
+
+FileSystemParams GetFilesTaskChild::GetRequestParams(
+    const nsString& aSerializedDOMPath, ErrorResult& aRv) const {
+  mFileSystem->AssertIsOnOwningThread();
+
+  nsAutoString path;
+  aRv = mTargetPath->GetPath(path);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return FileSystemGetFilesParams();
+  }
+
+  nsAutoString domPath;
+  mDirectory->GetPath(domPath, aRv);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return FileSystemGetFilesParams();
+  }
+
+  return FileSystemGetFilesParams(aSerializedDOMPath, path, domPath,
+                                  mRecursiveFlag);
+}
+
+void GetFilesTaskChild::SetSuccessRequestResult(
+    const FileSystemResponseValue& aValue, ErrorResult& aRv) {
+  mFileSystem->AssertIsOnOwningThread();
+  MOZ_ASSERT(aValue.type() ==
+             FileSystemResponseValue::TFileSystemFilesResponse);
+
+  FileSystemFilesResponse r = aValue;
+
+  if (!mTargetData.SetLength(r.data().Length(), mozilla::fallible_t())) {
+    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+    return;
+  }
+
+  nsCOMPtr<nsIGlobalObject> globalObject = mFileSystem->GetParentObject();
+  MOZ_ASSERT(globalObject);
+
+  for (uint32_t i = 0; i < r.data().Length(); ++i) {
+    const FileSystemFileResponse& data = r.data()[i];
+    RefPtr<BlobImpl> blobImpl = IPCBlobUtils::Deserialize(data.blob());
+    MOZ_ASSERT(blobImpl);
+
+    mTargetData[i] = File::Create(globalObject, blobImpl);
+    if (NS_WARN_IF(!mTargetData[i])) {
+      aRv.Throw(NS_ERROR_FAILURE);
+      return;
+    }
+  }
+}
+
+void GetFilesTaskChild::HandlerCallback() {
+  mFileSystem->AssertIsOnOwningThread();
+  if (mFileSystem->IsShutdown()) {
+    mPromise = nullptr;
+    return;
+  }
+
+  if (HasError()) {
+    mPromise->MaybeReject(NS_ERROR_DOM_INVALID_STATE_ERR);
+    mPromise = nullptr;
+    return;
+  }
+
+  mPromise->MaybeResolve(mTargetData);
+  mPromise = nullptr;
+}
+
+/**
+ * GetFilesTaskParent
+ */
+
+/* static */
+already_AddRefed<GetFilesTaskParent> GetFilesTaskParent::Create(
+    FileSystemBase* aFileSystem, const FileSystemGetFilesParams& aParam,
+    FileSystemRequestParent* aParent, ErrorResult& aRv) {
+  MOZ_ASSERT(XRE_IsParentProcess(), "Only call from parent process!");
+  mozilla::ipc::AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aFileSystem);
+
+  RefPtr<GetFilesTaskParent> task =
+      new GetFilesTaskParent(aFileSystem, aParam, aParent);
+
+  aRv = NS_NewLocalFile(aParam.realPath(), true,
+                        getter_AddRefs(task->mTargetPath));
+  if (NS_WARN_IF(aRv.Failed())) {
+    return nullptr;
+  }
+
+  return task.forget();
+}
+
+GetFilesTaskParent::GetFilesTaskParent(FileSystemBase* aFileSystem,
+                                       const FileSystemGetFilesParams& aParam,
+                                       FileSystemRequestParent* aParent)
+    : FileSystemTaskParentBase(aFileSystem, aParam, aParent),
+      GetFilesHelperBase(aParam.recursiveFlag()),
+      mDirectoryDOMPath(aParam.domPath()) {
+  MOZ_ASSERT(XRE_IsParentProcess(), "Only call from parent process!");
+  mozilla::ipc::AssertIsOnBackgroundThread();
+  MOZ_ASSERT(aFileSystem);
+}
+
+FileSystemResponseValue GetFilesTaskParent::GetSuccessRequestResult(
+    ErrorResult& aRv) const {
+  mozilla::ipc::AssertIsOnBackgroundThread();
+
+  FallibleTArray<FileSystemFileResponse> inputs;
+  if (!inputs.SetLength(mTargetBlobImplArray.Length(), mozilla::fallible_t())) {
+    FileSystemFilesResponse response;
+    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+    return response;
+  }
+
+  for (unsigned i = 0; i < mTargetBlobImplArray.Length(); i++) {
+    IPCBlob ipcBlob;
+    aRv = IPCBlobUtils::Serialize(mTargetBlobImplArray[i], ipcBlob);
+    if (NS_WARN_IF(aRv.Failed())) {
+      FileSystemFilesResponse response;
+      return response;
+    }
+
+    inputs[i] = FileSystemFileResponse(ipcBlob);
+  }
+
+  FileSystemFilesResponse response;
+  response.data() = std::move(inputs);
+  return response;
+}
+
+nsresult GetFilesTaskParent::IOWork() {
+  MOZ_ASSERT(XRE_IsParentProcess(), "Only call from parent process!");
+  MOZ_ASSERT(!NS_IsMainThread(), "Only call on I/O thread!");
+
+  if (mFileSystem->IsShutdown()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  bool exists;
+  nsresult rv = mTargetPath->Exists(&exists);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  if (!exists) {
+    return NS_OK;
+  }
+
+  bool isDir;
+  rv = mTargetPath->IsDirectory(&isDir);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  if (!isDir) {
+    return NS_ERROR_DOM_FILESYSTEM_TYPE_MISMATCH_ERR;
+  }
+
+  // Get isDirectory.
+  rv = ExploreDirectory(mDirectoryDOMPath, mTargetPath);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+nsresult GetFilesTaskParent::GetTargetPath(nsAString& aPath) const {
+  return mTargetPath->GetPath(aPath);
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/GetFilesTask.h b/dom/filesystem/GetFilesTask.h
new file mode 100644
index 0000000000..6f6f15e879
--- /dev/null
+++ b/dom/filesystem/GetFilesTask.h
@@ -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/. */
+
+#ifndef mozilla_dom_GetFilesTask_h
+#define mozilla_dom_GetFilesTask_h
+
+#include "mozilla/dom/Directory.h"
+#include "mozilla/dom/FileSystemTaskBase.h"
+#include "mozilla/dom/GetFilesHelper.h"
+
+namespace mozilla {
+class ErrorResult;
+
+namespace dom {
+
+class BlobImpl;
+class FileSystemGetFilesParams;
+
+class GetFilesTaskChild final : public FileSystemTaskChildBase {
+ public:
+  static already_AddRefed<GetFilesTaskChild> Create(FileSystemBase* aFileSystem,
+                                                    Directory* aDirectory,
+                                                    nsIFile* aTargetPath,
+                                                    bool aRecursiveFlag,
+                                                    ErrorResult& aRv);
+
+  virtual ~GetFilesTaskChild();
+
+  already_AddRefed<Promise> GetPromise();
+
+ private:
+  // If aDirectoryOnly is set, we should ensure that the target is a directory.
+  GetFilesTaskChild(nsIGlobalObject* aGlobalObject, FileSystemBase* aFileSystem,
+                    Directory* aDirectory, nsIFile* aTargetPath,
+                    bool aRecursiveFlag);
+
+  virtual FileSystemParams GetRequestParams(const nsString& aSerializedDOMPath,
+                                            ErrorResult& aRv) const override;
+
+  virtual void SetSuccessRequestResult(const FileSystemResponseValue& aValue,
+                                       ErrorResult& aRv) override;
+
+  virtual void HandlerCallback() override;
+
+  RefPtr<Promise> mPromise;
+  RefPtr<Directory> mDirectory;
+  nsCOMPtr<nsIFile> mTargetPath;
+  bool mRecursiveFlag;
+
+  // We store the fullpath and the dom path of Files.
+  FallibleTArray<RefPtr<File>> mTargetData;
+};
+
+class GetFilesTaskParent final : public FileSystemTaskParentBase,
+                                 public GetFilesHelperBase {
+ public:
+  static already_AddRefed<GetFilesTaskParent> Create(
+      FileSystemBase* aFileSystem, const FileSystemGetFilesParams& aParam,
+      FileSystemRequestParent* aParent, ErrorResult& aRv);
+
+  nsresult GetTargetPath(nsAString& aPath) const override;
+
+ private:
+  GetFilesTaskParent(FileSystemBase* aFileSystem,
+                     const FileSystemGetFilesParams& aParam,
+                     FileSystemRequestParent* aParent);
+
+  virtual FileSystemResponseValue GetSuccessRequestResult(
+      ErrorResult& aRv) const override;
+
+  virtual nsresult IOWork() override;
+
+  nsString mDirectoryDOMPath;
+  nsCOMPtr<nsIFile> mTargetPath;
+};
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // mozilla_dom_GetFilesTask_h
diff --git a/dom/filesystem/OSFileSystem.cpp b/dom/filesystem/OSFileSystem.cpp
new file mode 100644
index 0000000000..2322d07b93
--- /dev/null
+++ b/dom/filesystem/OSFileSystem.cpp
@@ -0,0 +1,88 @@
+/* -*- 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/OSFileSystem.h"
+
+#include "mozilla/dom/Directory.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/dom/FileSystemUtils.h"
+#include "nsIGlobalObject.h"
+#include "nsCOMPtr.h"
+#include "nsDebug.h"
+#include "nsIFile.h"
+
+namespace mozilla::dom {
+
+OSFileSystem::OSFileSystem(const nsAString& aRootDir) {
+  mLocalRootPath = aRootDir;
+}
+
+already_AddRefed<FileSystemBase> OSFileSystem::Clone() {
+  AssertIsOnOwningThread();
+
+  RefPtr<OSFileSystem> fs = new OSFileSystem(mLocalRootPath);
+  if (mGlobal) {
+    fs->Init(mGlobal);
+  }
+
+  return fs.forget();
+}
+
+void OSFileSystem::Init(nsIGlobalObject* aGlobal) {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(!mGlobal, "No duple Init() calls");
+  MOZ_ASSERT(aGlobal);
+
+  mGlobal = aGlobal;
+}
+
+nsIGlobalObject* OSFileSystem::GetParentObject() const {
+  AssertIsOnOwningThread();
+  return mGlobal;
+}
+
+bool OSFileSystem::IsSafeFile(nsIFile* aFile) const {
+  // The concept of "safe files" is specific to the Device Storage API where
+  // files are only "safe" if they're of a type that is appropriate for the
+  // area of device storage that is being used.
+  MOZ_CRASH("Don't use OSFileSystem with the Device Storage API");
+  return true;
+}
+
+bool OSFileSystem::IsSafeDirectory(Directory* aDir) const {
+  // The concept of "safe directory" is specific to the Device Storage API
+  // where a directory is only "safe" if it belongs to the area of device
+  // storage that it is being used with.
+  MOZ_CRASH("Don't use OSFileSystem with the Device Storage API");
+  return true;
+}
+
+void OSFileSystem::Unlink() {
+  AssertIsOnOwningThread();
+  mGlobal = nullptr;
+}
+
+void OSFileSystem::Traverse(nsCycleCollectionTraversalCallback& cb) {
+  AssertIsOnOwningThread();
+
+  OSFileSystem* tmp = this;
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mGlobal);
+}
+
+void OSFileSystem::SerializeDOMPath(nsAString& aOutput) const {
+  AssertIsOnOwningThread();
+  aOutput = mLocalRootPath;
+}
+
+/**
+ * OSFileSystemParent
+ */
+
+OSFileSystemParent::OSFileSystemParent(const nsAString& aRootDir) {
+  mLocalRootPath = aRootDir;
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/OSFileSystem.h b/dom/filesystem/OSFileSystem.h
new file mode 100644
index 0000000000..cb2ade7fc5
--- /dev/null
+++ b/dom/filesystem/OSFileSystem.h
@@ -0,0 +1,98 @@
+/* -*- 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_OSFileSystem_h
+#define mozilla_dom_OSFileSystem_h
+
+#include "mozilla/dom/FileSystemBase.h"
+
+namespace mozilla::dom {
+
+class OSFileSystem final : public FileSystemBase {
+ public:
+  explicit OSFileSystem(const nsAString& aRootDir);
+
+  void Init(nsIGlobalObject* aGlobal);
+
+  // Overrides FileSystemBase
+
+  virtual already_AddRefed<FileSystemBase> Clone() override;
+
+  virtual bool ShouldCreateDirectory() override {
+    MOZ_CRASH("This should not be called.");
+    // Because OSFileSystem should not be used when the creation of directories
+    // is needed. For that we have OSFileSystemParent.
+    return false;
+  }
+
+  virtual nsIGlobalObject* GetParentObject() const override;
+
+  virtual bool IsSafeFile(nsIFile* aFile) const override;
+
+  virtual bool IsSafeDirectory(Directory* aDir) const override;
+
+  virtual void SerializeDOMPath(nsAString& aOutput) const override;
+
+  // CC methods
+  virtual void Unlink() override;
+  virtual void Traverse(nsCycleCollectionTraversalCallback& cb) override;
+
+ private:
+  virtual ~OSFileSystem() = default;
+
+  nsCOMPtr<nsIGlobalObject> mGlobal;
+};
+
+class OSFileSystemParent final : public FileSystemBase {
+ public:
+  explicit OSFileSystemParent(const nsAString& aRootDir);
+
+  // Overrides FileSystemBase
+
+  virtual already_AddRefed<FileSystemBase> Clone() override {
+    MOZ_CRASH("This should not be called on the PBackground thread.");
+    return nullptr;
+  }
+
+  virtual bool ShouldCreateDirectory() override { return false; }
+
+  virtual nsIGlobalObject* GetParentObject() const override {
+    MOZ_CRASH("This should not be called on the PBackground thread.");
+    return nullptr;
+  }
+
+  virtual void GetDirectoryName(nsIFile* aFile, nsAString& aRetval,
+                                ErrorResult& aRv) const override {
+    MOZ_CRASH("This should not be called on the PBackground thread.");
+  }
+
+  virtual bool IsSafeFile(nsIFile* aFile) const override { return true; }
+
+  virtual bool IsSafeDirectory(Directory* aDir) const override {
+    MOZ_CRASH("This should not be called on the PBackground thread.");
+    return true;
+  }
+
+  virtual void SerializeDOMPath(nsAString& aOutput) const override {
+    MOZ_CRASH("This should not be called on the PBackground thread.");
+  }
+
+  // CC methods
+  virtual void Unlink() override {
+    MOZ_CRASH("This should not be called on the PBackground thread.");
+  }
+
+  virtual void Traverse(nsCycleCollectionTraversalCallback& cb) override {
+    MOZ_CRASH("This should not be called on the PBackground thread.");
+  }
+
+ private:
+  virtual ~OSFileSystemParent() = default;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_OSFileSystem_h
diff --git a/dom/filesystem/PFileSystemParams.ipdlh b/dom/filesystem/PFileSystemParams.ipdlh
new file mode 100644
index 0000000000..40b1e095f1
--- /dev/null
+++ b/dom/filesystem/PFileSystemParams.ipdlh
@@ -0,0 +1,48 @@
+/* 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/. */
+
+namespace mozilla {
+namespace dom {
+
+struct FileSystemGetDirectoryListingParams
+{
+  nsString filesystem;
+  nsString realPath;
+  nsString domPath;
+
+  // 'filters' could be an array rather than a semicolon separated string
+  // (we'd then use nsTArray<nsString> internally), but that is
+  // wasteful.  E10s requires us to pass the filters over as a string anyway,
+  // so avoiding using an array avoids serialization on the side passing the
+  // filters.  Since an nsString can share its buffer when copied,
+  // using that instead of nsTArray<nsString> makes copying the filters
+  // around in any given process a bit more efficient too, since copying a
+  // single nsString is cheaper than copying nsTArray member data and
+  // each nsString that it contains.
+  nsString filters;
+};
+
+struct FileSystemGetFilesParams
+{
+  nsString filesystem;
+  nsString realPath;
+  nsString domPath;
+  bool recursiveFlag;
+};
+
+struct FileSystemGetFileOrDirectoryParams
+{
+  nsString filesystem;
+  nsString realPath;
+};
+
+union FileSystemParams
+{
+  FileSystemGetDirectoryListingParams;
+  FileSystemGetFilesParams;
+  FileSystemGetFileOrDirectoryParams;
+};
+
+} // dom namespace
+} // mozilla namespace
diff --git a/dom/filesystem/PFileSystemRequest.ipdl b/dom/filesystem/PFileSystemRequest.ipdl
new file mode 100644
index 0000000000..3ae24e269b
--- /dev/null
+++ b/dom/filesystem/PFileSystemRequest.ipdl
@@ -0,0 +1,77 @@
+/* -*- Mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; tab-width: 40 -*- */
+/* vim: set ts=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 protocol PBackground;
+
+include IPCBlob;
+
+include "mozilla/dom/FileSystemTaskBase.h";
+
+namespace mozilla {
+namespace dom {
+
+struct FileSystemFileResponse
+{
+  IPCBlob blob;
+};
+
+struct FileSystemDirectoryResponse
+{
+  nsString realPath;
+};
+
+struct FileSystemDirectoryListingResponseFile
+{
+  IPCBlob blob;
+};
+
+struct FileSystemDirectoryListingResponseDirectory
+{
+  // This is the full real path for the directory that we are sending via IPC.
+  nsString directoryRealPath;
+};
+
+union FileSystemDirectoryListingResponseData
+{
+  FileSystemDirectoryListingResponseFile;
+  FileSystemDirectoryListingResponseDirectory;
+};
+
+struct FileSystemDirectoryListingResponse
+{
+  FileSystemDirectoryListingResponseData[] data;
+};
+
+struct FileSystemFilesResponse
+{
+  FileSystemFileResponse[] data;
+};
+
+struct FileSystemErrorResponse
+{
+  nsresult error;
+};
+
+union FileSystemResponseValue
+{
+  FileSystemDirectoryResponse;
+  FileSystemDirectoryListingResponse;
+  FileSystemFileResponse;
+  FileSystemFilesResponse;
+  FileSystemErrorResponse;
+};
+
+[ChildImpl="FileSystemTaskChildBase"]
+protocol PFileSystemRequest
+{
+  manager PBackground;
+
+child:
+  async __delete__(FileSystemResponseValue response);
+};
+
+} // namespace dom
+} // namespace mozilla
diff --git a/dom/filesystem/compat/CallbackRunnables.cpp b/dom/filesystem/compat/CallbackRunnables.cpp
new file mode 100644
index 0000000000..cbdd2f2f56
--- /dev/null
+++ b/dom/filesystem/compat/CallbackRunnables.cpp
@@ -0,0 +1,280 @@
+/* -*- 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 "CallbackRunnables.h"
+#include "mozilla/dom/Directory.h"
+#include "mozilla/dom/DirectoryBinding.h"
+#include "mozilla/dom/DOMException.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/dom/FileBinding.h"
+#include "mozilla/dom/FileSystem.h"
+#include "mozilla/dom/FileSystemDirectoryReaderBinding.h"
+#include "mozilla/dom/FileSystemFileEntry.h"
+#include "mozilla/dom/FileSystemUtils.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/Unused.h"
+#include "nsIGlobalObject.h"
+#include "nsIFile.h"
+#include "nsPIDOMWindow.h"
+
+#include "../GetFileOrDirectoryTask.h"
+
+namespace mozilla::dom {
+
+EntryCallbackRunnable::EntryCallbackRunnable(FileSystemEntryCallback* aCallback,
+                                             FileSystemEntry* aEntry)
+    : Runnable("EntryCallbackRunnable"), mCallback(aCallback), mEntry(aEntry) {
+  MOZ_ASSERT(aCallback);
+  MOZ_ASSERT(aEntry);
+}
+
+NS_IMETHODIMP
+EntryCallbackRunnable::Run() {
+  mCallback->Call(*mEntry);
+  return NS_OK;
+}
+
+ErrorCallbackRunnable::ErrorCallbackRunnable(nsIGlobalObject* aGlobalObject,
+                                             ErrorCallback* aCallback,
+                                             nsresult aError)
+    : Runnable("ErrorCallbackRunnable"),
+      mGlobal(aGlobalObject),
+      mCallback(aCallback),
+      mError(aError) {
+  MOZ_ASSERT(aGlobalObject);
+  MOZ_ASSERT(aCallback);
+  MOZ_ASSERT(NS_FAILED(aError));
+}
+
+NS_IMETHODIMP
+ErrorCallbackRunnable::Run() {
+  RefPtr<DOMException> exception = DOMException::Create(mError);
+  mCallback->Call(*exception);
+  return NS_OK;
+}
+
+EmptyEntriesCallbackRunnable::EmptyEntriesCallbackRunnable(
+    FileSystemEntriesCallback* aCallback)
+    : Runnable("EmptyEntriesCallbackRunnable"), mCallback(aCallback) {
+  MOZ_ASSERT(aCallback);
+}
+
+NS_IMETHODIMP
+EmptyEntriesCallbackRunnable::Run() {
+  Sequence<OwningNonNull<FileSystemEntry>> sequence;
+  mCallback->Call(sequence);
+  return NS_OK;
+}
+
+GetEntryHelper::GetEntryHelper(FileSystemDirectoryEntry* aParentEntry,
+                               Directory* aDirectory,
+                               nsTArray<nsString>& aParts,
+                               FileSystem* aFileSystem,
+                               FileSystemEntryCallback* aSuccessCallback,
+                               ErrorCallback* aErrorCallback,
+                               FileSystemDirectoryEntry::GetInternalType aType)
+    : mParentEntry(aParentEntry),
+      mDirectory(aDirectory),
+      mParts(aParts.Clone()),
+      mFileSystem(aFileSystem),
+      mSuccessCallback(aSuccessCallback),
+      mErrorCallback(aErrorCallback),
+      mType(aType) {
+  MOZ_ASSERT(aParentEntry);
+  MOZ_ASSERT(aDirectory);
+  MOZ_ASSERT(!aParts.IsEmpty());
+  MOZ_ASSERT(aFileSystem);
+  MOZ_ASSERT(aSuccessCallback || aErrorCallback);
+}
+
+GetEntryHelper::~GetEntryHelper() = default;
+
+namespace {
+
+nsresult DOMPathToRealPath(Directory* aDirectory, const nsAString& aPath,
+                           nsIFile** aFile) {
+  nsString relativePath;
+  relativePath = aPath;
+
+  // Trim white spaces.
+  static const char kWhitespace[] = "\b\t\r\n ";
+  relativePath.Trim(kWhitespace);
+
+  nsTArray<nsString> parts;
+  if (!FileSystemUtils::IsValidRelativeDOMPath(relativePath, parts)) {
+    return NS_ERROR_DOM_FILESYSTEM_INVALID_PATH_ERR;
+  }
+
+  nsCOMPtr<nsIFile> file;
+  nsresult rv = aDirectory->GetInternalNsIFile()->Clone(getter_AddRefs(file));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  for (uint32_t i = 0; i < parts.Length(); ++i) {
+    rv = file->AppendRelativePath(parts[i]);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+  }
+
+  file.forget(aFile);
+  return NS_OK;
+}
+
+}  // namespace
+
+void GetEntryHelper::Run() {
+  MOZ_ASSERT(!mParts.IsEmpty());
+
+  nsCOMPtr<nsIFile> realPath;
+  nsresult error =
+      DOMPathToRealPath(mDirectory, mParts[0], getter_AddRefs(realPath));
+
+  ErrorResult rv;
+  RefPtr<FileSystemBase> fs = mDirectory->GetFileSystem(rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    rv.SuppressException();
+    Error(NS_ERROR_DOM_INVALID_STATE_ERR);
+    return;
+  }
+
+  RefPtr<GetFileOrDirectoryTaskChild> task =
+      GetFileOrDirectoryTaskChild::Create(fs, realPath, rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    rv.SuppressException();
+    Error(NS_ERROR_DOM_INVALID_STATE_ERR);
+    return;
+  }
+
+  task->SetError(error);
+  task->Start();
+
+  RefPtr<Promise> promise = task->GetPromise();
+
+  mParts.RemoveElementAt(0);
+  promise->AppendNativeHandler(this);
+}
+
+void GetEntryHelper::ResolvedCallback(JSContext* aCx,
+                                      JS::Handle<JS::Value> aValue,
+                                      ErrorResult& aRv) {
+  if (NS_WARN_IF(!aValue.isObject())) {
+    return;
+  }
+
+  JS::Rooted<JSObject*> obj(aCx, &aValue.toObject());
+
+  // This is not the last part of the path.
+  if (!mParts.IsEmpty()) {
+    ContinueRunning(obj);
+    return;
+  }
+
+  CompleteOperation(obj);
+}
+
+void GetEntryHelper::CompleteOperation(JSObject* aObj) {
+  MOZ_ASSERT(mParts.IsEmpty());
+
+  if (mType == FileSystemDirectoryEntry::eGetFile) {
+    RefPtr<File> file;
+    if (NS_FAILED(UNWRAP_OBJECT(File, aObj, file))) {
+      Error(NS_ERROR_DOM_TYPE_MISMATCH_ERR);
+      return;
+    }
+
+    RefPtr<FileSystemFileEntry> entry = new FileSystemFileEntry(
+        mParentEntry->GetParentObject(), file, mParentEntry, mFileSystem);
+    mSuccessCallback->Call(*entry);
+    return;
+  }
+
+  MOZ_ASSERT(mType == FileSystemDirectoryEntry::eGetDirectory);
+
+  RefPtr<Directory> directory;
+  if (NS_FAILED(UNWRAP_OBJECT(Directory, aObj, directory))) {
+    Error(NS_ERROR_DOM_TYPE_MISMATCH_ERR);
+    return;
+  }
+
+  RefPtr<FileSystemDirectoryEntry> entry = new FileSystemDirectoryEntry(
+      mParentEntry->GetParentObject(), directory, mParentEntry, mFileSystem);
+  mSuccessCallback->Call(*entry);
+}
+
+void GetEntryHelper::ContinueRunning(JSObject* aObj) {
+  MOZ_ASSERT(!mParts.IsEmpty());
+
+  RefPtr<Directory> directory;
+  if (NS_FAILED(UNWRAP_OBJECT(Directory, aObj, directory))) {
+    Error(NS_ERROR_DOM_TYPE_MISMATCH_ERR);
+    return;
+  }
+
+  RefPtr<FileSystemDirectoryEntry> entry = new FileSystemDirectoryEntry(
+      mParentEntry->GetParentObject(), directory, mParentEntry, mFileSystem);
+
+  // Update the internal values.
+  mParentEntry = entry;
+  mDirectory = directory;
+
+  Run();
+}
+
+void GetEntryHelper::RejectedCallback(JSContext* aCx,
+                                      JS::Handle<JS::Value> aValue,
+                                      ErrorResult& aRv) {
+  Error(NS_ERROR_DOM_NOT_FOUND_ERR);
+}
+
+void GetEntryHelper::Error(nsresult aError) {
+  MOZ_ASSERT(NS_FAILED(aError));
+
+  if (mErrorCallback) {
+    RefPtr<ErrorCallbackRunnable> runnable = new ErrorCallbackRunnable(
+        mParentEntry->GetParentObject(), mErrorCallback, aError);
+
+    FileSystemUtils::DispatchRunnable(mParentEntry->GetParentObject(),
+                                      runnable.forget());
+  }
+}
+
+NS_IMPL_ISUPPORTS0(GetEntryHelper);
+
+/* static */
+void FileSystemEntryCallbackHelper::Call(
+    nsIGlobalObject* aGlobalObject,
+    const Optional<OwningNonNull<FileSystemEntryCallback>>& aEntryCallback,
+    FileSystemEntry* aEntry) {
+  MOZ_ASSERT(aGlobalObject);
+  MOZ_ASSERT(aEntry);
+
+  if (aEntryCallback.WasPassed()) {
+    RefPtr<EntryCallbackRunnable> runnable =
+        new EntryCallbackRunnable(&aEntryCallback.Value(), aEntry);
+
+    FileSystemUtils::DispatchRunnable(aGlobalObject, runnable.forget());
+  }
+}
+
+/* static */
+void ErrorCallbackHelper::Call(
+    nsIGlobalObject* aGlobal,
+    const Optional<OwningNonNull<ErrorCallback>>& aErrorCallback,
+    nsresult aError) {
+  MOZ_ASSERT(aGlobal);
+  MOZ_ASSERT(NS_FAILED(aError));
+
+  if (aErrorCallback.WasPassed()) {
+    RefPtr<ErrorCallbackRunnable> runnable =
+        new ErrorCallbackRunnable(aGlobal, &aErrorCallback.Value(), aError);
+
+    FileSystemUtils::DispatchRunnable(aGlobal, runnable.forget());
+  }
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/compat/CallbackRunnables.h b/dom/filesystem/compat/CallbackRunnables.h
new file mode 100644
index 0000000000..e2e1c47913
--- /dev/null
+++ b/dom/filesystem/compat/CallbackRunnables.h
@@ -0,0 +1,118 @@
+/* -*- 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_ErrorCallbackRunnable_h
+#define mozilla_dom_ErrorCallbackRunnable_h
+
+#include "FileSystemDirectoryEntry.h"
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/PromiseNativeHandler.h"
+#include "nsThreadUtils.h"
+
+class nsIGlobalObject;
+
+namespace mozilla::dom {
+
+class FileSystemEntriesCallback;
+
+class EntryCallbackRunnable final : public Runnable {
+ public:
+  EntryCallbackRunnable(FileSystemEntryCallback* aCallback,
+                        FileSystemEntry* aEntry);
+
+  // MOZ_CAN_RUN_SCRIPT_BOUNDARY until Runnable::Run is MOZ_CAN_RUN_SCRIPT.  See
+  // bug 1535398.
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY NS_IMETHOD Run() override;
+
+ private:
+  const RefPtr<FileSystemEntryCallback> mCallback;
+  const RefPtr<FileSystemEntry> mEntry;
+};
+
+class ErrorCallbackRunnable final : public Runnable {
+ public:
+  ErrorCallbackRunnable(nsIGlobalObject* aGlobalObject,
+                        ErrorCallback* aCallback, nsresult aError);
+
+  // MOZ_CAN_RUN_SCRIPT_BOUNDARY until Runnable::Run is MOZ_CAN_RUN_SCRIPT.  See
+  // bug 1535398.
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY NS_IMETHOD Run() override;
+
+ private:
+  nsCOMPtr<nsIGlobalObject> mGlobal;
+  const RefPtr<ErrorCallback> mCallback;
+  nsresult mError;
+};
+
+class EmptyEntriesCallbackRunnable final : public Runnable {
+ public:
+  explicit EmptyEntriesCallbackRunnable(FileSystemEntriesCallback* aCallback);
+
+  // MOZ_CAN_RUN_SCRIPT_BOUNDARY until Runnable::Run is MOZ_CAN_RUN_SCRIPT.  See
+  // bug 1535398.
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY NS_IMETHOD Run() override;
+
+ private:
+  const RefPtr<FileSystemEntriesCallback> mCallback;
+};
+
+class GetEntryHelper final : public PromiseNativeHandler {
+ public:
+  NS_DECL_ISUPPORTS
+
+  GetEntryHelper(FileSystemDirectoryEntry* aParentEntry, Directory* aDirectory,
+                 nsTArray<nsString>& aParts, FileSystem* aFileSystem,
+                 FileSystemEntryCallback* aSuccessCallback,
+                 ErrorCallback* aErrorCallback,
+                 FileSystemDirectoryEntry::GetInternalType aType);
+
+  void Run();
+
+  MOZ_CAN_RUN_SCRIPT
+  virtual void ResolvedCallback(JSContext* aCx, JS::Handle<JS::Value> aValue,
+                                ErrorResult& aRv) override;
+
+  virtual void RejectedCallback(JSContext* aCx, JS::Handle<JS::Value> aValue,
+                                ErrorResult& aRv) override;
+
+ private:
+  ~GetEntryHelper();
+
+  void Error(nsresult aError);
+
+  void ContinueRunning(JSObject* aObj);
+
+  MOZ_CAN_RUN_SCRIPT void CompleteOperation(JSObject* aObj);
+
+  RefPtr<FileSystemDirectoryEntry> mParentEntry;
+  RefPtr<Directory> mDirectory;
+  nsTArray<nsString> mParts;
+  RefPtr<FileSystem> mFileSystem;
+
+  const RefPtr<FileSystemEntryCallback> mSuccessCallback;
+  RefPtr<ErrorCallback> mErrorCallback;
+
+  FileSystemDirectoryEntry::GetInternalType mType;
+};
+
+class FileSystemEntryCallbackHelper {
+ public:
+  static void Call(
+      nsIGlobalObject* aGlobalObject,
+      const Optional<OwningNonNull<FileSystemEntryCallback>>& aEntryCallback,
+      FileSystemEntry* aEntry);
+};
+
+class ErrorCallbackHelper {
+ public:
+  static void Call(nsIGlobalObject* aGlobal,
+                   const Optional<OwningNonNull<ErrorCallback>>& aErrorCallback,
+                   nsresult aError);
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_CallbackRunnables_h
diff --git a/dom/filesystem/compat/FileSystem.cpp b/dom/filesystem/compat/FileSystem.cpp
new file mode 100644
index 0000000000..734b3ec600
--- /dev/null
+++ b/dom/filesystem/compat/FileSystem.cpp
@@ -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/. */
+
+#include "FileSystem.h"
+#include "FileSystemRootDirectoryEntry.h"
+#include "mozilla/dom/FileSystemBinding.h"
+#include "nsIDUtils.h"
+
+namespace mozilla::dom {
+
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(FileSystem, mParent, mRoot)
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(FileSystem)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(FileSystem)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(FileSystem)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+/* static */
+already_AddRefed<FileSystem> FileSystem::Create(nsIGlobalObject* aGlobalObject)
+
+{
+  MOZ_ASSERT(aGlobalObject);
+
+  nsID id;
+  nsresult rv = nsID::GenerateUUIDInPlace(id);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nullptr;
+  }
+
+  NSID_TrimBracketsUTF16 name(id);
+
+  RefPtr<FileSystem> fs = new FileSystem(aGlobalObject, name);
+
+  return fs.forget();
+}
+
+FileSystem::FileSystem(nsIGlobalObject* aGlobal, const nsAString& aName)
+    : mParent(aGlobal), mName(aName) {
+  MOZ_ASSERT(aGlobal);
+}
+
+FileSystem::~FileSystem() = default;
+
+JSObject* FileSystem::WrapObject(JSContext* aCx,
+                                 JS::Handle<JSObject*> aGivenProto) {
+  return FileSystem_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+void FileSystem::CreateRoot(const Sequence<RefPtr<FileSystemEntry>>& aEntries) {
+  MOZ_ASSERT(!mRoot);
+  mRoot = new FileSystemRootDirectoryEntry(mParent, aEntries, this);
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/compat/FileSystem.h b/dom/filesystem/compat/FileSystem.h
new file mode 100644
index 0000000000..92cb563ef4
--- /dev/null
+++ b/dom/filesystem/compat/FileSystem.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_dom_FileSystem_h
+#define mozilla_dom_FileSystem_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/dom/BindingDeclarations.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsWrapperCache.h"
+
+class nsIGlobalObject;
+
+namespace mozilla::dom {
+
+class FileSystemDirectoryEntry;
+class FileSystemEntry;
+class OwningFileOrDirectory;
+
+class FileSystem final : public nsISupports, public nsWrapperCache {
+ public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(FileSystem)
+
+  static already_AddRefed<FileSystem> Create(nsIGlobalObject* aGlobalObject);
+
+  nsIGlobalObject* GetParentObject() const { return mParent; }
+
+  virtual JSObject* WrapObject(JSContext* aCx,
+                               JS::Handle<JSObject*> aGivenProto) override;
+
+  void GetName(nsAString& aName) const { aName = mName; }
+
+  FileSystemDirectoryEntry* Root() const { return mRoot; }
+
+  void CreateRoot(const Sequence<RefPtr<FileSystemEntry>>& aEntries);
+
+ private:
+  explicit FileSystem(nsIGlobalObject* aGlobalObject, const nsAString& aName);
+  ~FileSystem();
+
+  nsCOMPtr<nsIGlobalObject> mParent;
+  RefPtr<FileSystemDirectoryEntry> mRoot;
+  nsString mName;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_FileSystem_h
diff --git a/dom/filesystem/compat/FileSystemDirectoryEntry.cpp b/dom/filesystem/compat/FileSystemDirectoryEntry.cpp
new file mode 100644
index 0000000000..7358f997f0
--- /dev/null
+++ b/dom/filesystem/compat/FileSystemDirectoryEntry.cpp
@@ -0,0 +1,92 @@
+/* -*- 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 "FileSystemDirectoryEntry.h"
+#include "CallbackRunnables.h"
+#include "FileSystemDirectoryReader.h"
+#include "mozilla/dom/Directory.h"
+#include "mozilla/dom/FileSystemDirectoryEntryBinding.h"
+#include "mozilla/dom/FileSystemUtils.h"
+
+namespace mozilla::dom {
+
+NS_IMPL_CYCLE_COLLECTION_INHERITED(FileSystemDirectoryEntry, FileSystemEntry,
+                                   mDirectory)
+
+NS_IMPL_ADDREF_INHERITED(FileSystemDirectoryEntry, FileSystemEntry)
+NS_IMPL_RELEASE_INHERITED(FileSystemDirectoryEntry, FileSystemEntry)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(FileSystemDirectoryEntry)
+NS_INTERFACE_MAP_END_INHERITING(FileSystemEntry)
+
+FileSystemDirectoryEntry::FileSystemDirectoryEntry(
+    nsIGlobalObject* aGlobal, Directory* aDirectory,
+    FileSystemDirectoryEntry* aParentEntry, FileSystem* aFileSystem)
+    : FileSystemEntry(aGlobal, aParentEntry, aFileSystem),
+      mDirectory(aDirectory) {
+  MOZ_ASSERT(aGlobal);
+}
+
+FileSystemDirectoryEntry::~FileSystemDirectoryEntry() = default;
+
+JSObject* FileSystemDirectoryEntry::WrapObject(
+    JSContext* aCx, JS::Handle<JSObject*> aGivenProto) {
+  return FileSystemDirectoryEntry_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+void FileSystemDirectoryEntry::GetName(nsAString& aName,
+                                       ErrorResult& aRv) const {
+  MOZ_ASSERT(mDirectory);
+  mDirectory->GetName(aName, aRv);
+}
+
+void FileSystemDirectoryEntry::GetFullPath(nsAString& aPath,
+                                           ErrorResult& aRv) const {
+  MOZ_ASSERT(mDirectory);
+  mDirectory->GetPath(aPath, aRv);
+}
+
+already_AddRefed<FileSystemDirectoryReader>
+FileSystemDirectoryEntry::CreateReader() {
+  MOZ_ASSERT(mDirectory);
+
+  RefPtr<FileSystemDirectoryReader> reader =
+      new FileSystemDirectoryReader(this, Filesystem(), mDirectory);
+  return reader.forget();
+}
+
+void FileSystemDirectoryEntry::GetInternal(
+    const nsAString& aPath, const FileSystemFlags& aFlag,
+    const Optional<OwningNonNull<FileSystemEntryCallback>>& aSuccessCallback,
+    const Optional<OwningNonNull<ErrorCallback>>& aErrorCallback,
+    GetInternalType aType) {
+  MOZ_ASSERT(mDirectory);
+
+  if (!aSuccessCallback.WasPassed() && !aErrorCallback.WasPassed()) {
+    return;
+  }
+
+  if (aFlag.mCreate) {
+    ErrorCallbackHelper::Call(GetParentObject(), aErrorCallback,
+                              NS_ERROR_DOM_SECURITY_ERR);
+    return;
+  }
+
+  nsTArray<nsString> parts;
+  if (!FileSystemUtils::IsValidRelativeDOMPath(aPath, parts)) {
+    ErrorCallbackHelper::Call(GetParentObject(), aErrorCallback,
+                              NS_ERROR_DOM_NOT_FOUND_ERR);
+    return;
+  }
+
+  RefPtr<GetEntryHelper> helper = new GetEntryHelper(
+      this, mDirectory, parts, Filesystem(),
+      aSuccessCallback.WasPassed() ? &aSuccessCallback.Value() : nullptr,
+      aErrorCallback.WasPassed() ? &aErrorCallback.Value() : nullptr, aType);
+  helper->Run();
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/compat/FileSystemDirectoryEntry.h b/dom/filesystem/compat/FileSystemDirectoryEntry.h
new file mode 100644
index 0000000000..1b772691e1
--- /dev/null
+++ b/dom/filesystem/compat/FileSystemDirectoryEntry.h
@@ -0,0 +1,73 @@
+/* -*- 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_FileSystemDirectoryEntry_h
+#define mozilla_dom_FileSystemDirectoryEntry_h
+
+#include "mozilla/dom/FileSystemEntry.h"
+
+namespace mozilla::dom {
+
+class Directory;
+class FileSystemDirectoryReader;
+
+class FileSystemDirectoryEntry : public FileSystemEntry {
+ public:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(FileSystemDirectoryEntry,
+                                           FileSystemEntry)
+
+  FileSystemDirectoryEntry(nsIGlobalObject* aGlobalObject,
+                           Directory* aDirectory,
+                           FileSystemDirectoryEntry* aParentEntry,
+                           FileSystem* aFileSystem);
+
+  virtual JSObject* WrapObject(JSContext* aCx,
+                               JS::Handle<JSObject*> aGivenProto) override;
+
+  virtual bool IsDirectory() const override { return true; }
+
+  virtual void GetName(nsAString& aName, ErrorResult& aRv) const override;
+
+  virtual void GetFullPath(nsAString& aFullPath,
+                           ErrorResult& aRv) const override;
+
+  virtual already_AddRefed<FileSystemDirectoryReader> CreateReader();
+
+  void GetFile(
+      const Optional<nsAString>& aPath, const FileSystemFlags& aFlag,
+      const Optional<OwningNonNull<FileSystemEntryCallback>>& aSuccessCallback,
+      const Optional<OwningNonNull<ErrorCallback>>& aErrorCallback) {
+    GetInternal(aPath.WasPassed() ? aPath.Value() : u""_ns, aFlag,
+                aSuccessCallback, aErrorCallback, eGetFile);
+  }
+
+  void GetDirectory(
+      const Optional<nsAString>& aPath, const FileSystemFlags& aFlag,
+      const Optional<OwningNonNull<FileSystemEntryCallback>>& aSuccessCallback,
+      const Optional<OwningNonNull<ErrorCallback>>& aErrorCallback) {
+    GetInternal(aPath.WasPassed() ? aPath.Value() : u""_ns, aFlag,
+                aSuccessCallback, aErrorCallback, eGetDirectory);
+  }
+
+  enum GetInternalType { eGetFile, eGetDirectory };
+
+  virtual void GetInternal(
+      const nsAString& aPath, const FileSystemFlags& aFlag,
+      const Optional<OwningNonNull<FileSystemEntryCallback>>& aSuccessCallback,
+      const Optional<OwningNonNull<ErrorCallback>>& aErrorCallback,
+      GetInternalType aType);
+
+ protected:
+  virtual ~FileSystemDirectoryEntry();
+
+ private:
+  RefPtr<Directory> mDirectory;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_FileSystemDirectoryEntry_h
diff --git a/dom/filesystem/compat/FileSystemDirectoryReader.cpp b/dom/filesystem/compat/FileSystemDirectoryReader.cpp
new file mode 100644
index 0000000000..533faae413
--- /dev/null
+++ b/dom/filesystem/compat/FileSystemDirectoryReader.cpp
@@ -0,0 +1,181 @@
+/* -*- 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 "FileSystemDirectoryReader.h"
+#include "CallbackRunnables.h"
+#include "FileSystemFileEntry.h"
+#include "js/Array.h"               // JS::NewArrayObject
+#include "js/PropertyAndElement.h"  // JS_GetElement
+#include "mozilla/dom/FileBinding.h"
+#include "mozilla/dom/FileSystem.h"
+#include "mozilla/dom/FileSystemDirectoryReaderBinding.h"
+#include "mozilla/dom/FileSystemUtils.h"
+#include "mozilla/dom/Directory.h"
+#include "mozilla/dom/DirectoryBinding.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/dom/PromiseNativeHandler.h"
+
+namespace mozilla::dom {
+
+namespace {
+
+class PromiseHandler final : public PromiseNativeHandler {
+ public:
+  NS_DECL_ISUPPORTS
+
+  PromiseHandler(FileSystemDirectoryEntry* aParentEntry,
+                 FileSystem* aFileSystem,
+                 FileSystemEntriesCallback* aSuccessCallback,
+                 ErrorCallback* aErrorCallback)
+      : mParentEntry(aParentEntry),
+        mFileSystem(aFileSystem),
+        mSuccessCallback(aSuccessCallback),
+        mErrorCallback(aErrorCallback) {
+    MOZ_ASSERT(aParentEntry);
+    MOZ_ASSERT(aFileSystem);
+    MOZ_ASSERT(aSuccessCallback);
+  }
+
+  MOZ_CAN_RUN_SCRIPT
+  virtual void ResolvedCallback(JSContext* aCx, JS::Handle<JS::Value> aValue,
+                                ErrorResult& aRv) override {
+    if (NS_WARN_IF(!aValue.isObject())) {
+      return;
+    }
+
+    JS::Rooted<JSObject*> obj(aCx, &aValue.toObject());
+
+    uint32_t length;
+    if (NS_WARN_IF(!JS::GetArrayLength(aCx, obj, &length))) {
+      return;
+    }
+
+    Sequence<OwningNonNull<FileSystemEntry>> sequence;
+    if (NS_WARN_IF(!sequence.SetLength(length, fallible))) {
+      return;
+    }
+
+    for (uint32_t i = 0; i < length; ++i) {
+      JS::Rooted<JS::Value> value(aCx);
+      if (NS_WARN_IF(!JS_GetElement(aCx, obj, i, &value))) {
+        return;
+      }
+
+      if (NS_WARN_IF(!value.isObject())) {
+        return;
+      }
+
+      JS::Rooted<JSObject*> valueObj(aCx, &value.toObject());
+
+      RefPtr<File> file;
+      if (NS_SUCCEEDED(UNWRAP_OBJECT(File, valueObj, file))) {
+        RefPtr<FileSystemFileEntry> entry = new FileSystemFileEntry(
+            mParentEntry->GetParentObject(), file, mParentEntry, mFileSystem);
+        sequence[i] = entry;
+        continue;
+      }
+
+      RefPtr<Directory> directory;
+      if (NS_WARN_IF(
+              NS_FAILED(UNWRAP_OBJECT(Directory, valueObj, directory)))) {
+        return;
+      }
+
+      RefPtr<FileSystemDirectoryEntry> entry =
+          new FileSystemDirectoryEntry(mParentEntry->GetParentObject(),
+                                       directory, mParentEntry, mFileSystem);
+      sequence[i] = entry;
+    }
+
+    mSuccessCallback->Call(sequence);
+  }
+
+  virtual void RejectedCallback(JSContext* aCx, JS::Handle<JS::Value> aValue,
+                                ErrorResult& aRv) override {
+    if (mErrorCallback) {
+      RefPtr<ErrorCallbackRunnable> runnable = new ErrorCallbackRunnable(
+          mParentEntry->GetParentObject(), mErrorCallback,
+          NS_ERROR_DOM_INVALID_STATE_ERR);
+
+      FileSystemUtils::DispatchRunnable(mParentEntry->GetParentObject(),
+                                        runnable.forget());
+    }
+  }
+
+ private:
+  ~PromiseHandler() = default;
+
+  RefPtr<FileSystemDirectoryEntry> mParentEntry;
+  RefPtr<FileSystem> mFileSystem;
+  const RefPtr<FileSystemEntriesCallback> mSuccessCallback;
+  RefPtr<ErrorCallback> mErrorCallback;
+};
+
+NS_IMPL_ISUPPORTS0(PromiseHandler);
+
+}  // anonymous namespace
+
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(FileSystemDirectoryReader, mParentEntry,
+                                      mDirectory, mFileSystem)
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(FileSystemDirectoryReader)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(FileSystemDirectoryReader)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(FileSystemDirectoryReader)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+FileSystemDirectoryReader::FileSystemDirectoryReader(
+    FileSystemDirectoryEntry* aParentEntry, FileSystem* aFileSystem,
+    Directory* aDirectory)
+    : mParentEntry(aParentEntry),
+      mFileSystem(aFileSystem),
+      mDirectory(aDirectory),
+      mAlreadyRead(false) {
+  MOZ_ASSERT(aParentEntry);
+  MOZ_ASSERT(aFileSystem);
+}
+
+FileSystemDirectoryReader::~FileSystemDirectoryReader() = default;
+
+JSObject* FileSystemDirectoryReader::WrapObject(
+    JSContext* aCx, JS::Handle<JSObject*> aGivenProto) {
+  return FileSystemDirectoryReader_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+void FileSystemDirectoryReader::ReadEntries(
+    FileSystemEntriesCallback& aSuccessCallback,
+    const Optional<OwningNonNull<ErrorCallback>>& aErrorCallback,
+    ErrorResult& aRv) {
+  MOZ_ASSERT(mDirectory);
+
+  if (mAlreadyRead) {
+    RefPtr<EmptyEntriesCallbackRunnable> runnable =
+        new EmptyEntriesCallbackRunnable(&aSuccessCallback);
+
+    FileSystemUtils::DispatchRunnable(GetParentObject(), runnable.forget());
+    return;
+  }
+
+  // This object can be used only once.
+  mAlreadyRead = true;
+
+  ErrorResult rv;
+  RefPtr<Promise> promise = mDirectory->GetFilesAndDirectories(rv);
+  if (NS_WARN_IF(rv.Failed())) {
+    ErrorCallbackHelper::Call(GetParentObject(), aErrorCallback,
+                              rv.StealNSResult());
+    return;
+  }
+
+  RefPtr<PromiseHandler> handler = new PromiseHandler(
+      mParentEntry, mFileSystem, &aSuccessCallback,
+      aErrorCallback.WasPassed() ? &aErrorCallback.Value() : nullptr);
+  promise->AppendNativeHandler(handler);
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/compat/FileSystemDirectoryReader.h b/dom/filesystem/compat/FileSystemDirectoryReader.h
new file mode 100644
index 0000000000..90274943b4
--- /dev/null
+++ b/dom/filesystem/compat/FileSystemDirectoryReader.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_FileSystemDirectoryReader_h
+#define mozilla_dom_FileSystemDirectoryReader_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/FileSystemDirectoryEntry.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsWrapperCache.h"
+
+namespace mozilla {
+class ErrorResult;
+
+namespace dom {
+
+class Directory;
+class FileSystem;
+class FileSystemEntriesCallback;
+
+class FileSystemDirectoryReader : public nsISupports, public nsWrapperCache {
+ public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(FileSystemDirectoryReader)
+
+  explicit FileSystemDirectoryReader(FileSystemDirectoryEntry* aDirectoryEntry,
+                                     FileSystem* aFileSystem,
+                                     Directory* aDirectory);
+
+  nsIGlobalObject* GetParentObject() const {
+    return mParentEntry->GetParentObject();
+  }
+
+  virtual JSObject* WrapObject(JSContext* aCx,
+                               JS::Handle<JSObject*> aGivenProto) override;
+
+  virtual void ReadEntries(
+      FileSystemEntriesCallback& aSuccessCallback,
+      const Optional<OwningNonNull<ErrorCallback>>& aErrorCallback,
+      ErrorResult& aRv);
+
+ protected:
+  virtual ~FileSystemDirectoryReader();
+
+ private:
+  RefPtr<FileSystemDirectoryEntry> mParentEntry;
+  RefPtr<FileSystem> mFileSystem;
+  RefPtr<Directory> mDirectory;
+
+  bool mAlreadyRead;
+};
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // mozilla_dom_FileSystemDirectoryReader_h
diff --git a/dom/filesystem/compat/FileSystemEntry.cpp b/dom/filesystem/compat/FileSystemEntry.cpp
new file mode 100644
index 0000000000..3a69e2537a
--- /dev/null
+++ b/dom/filesystem/compat/FileSystemEntry.cpp
@@ -0,0 +1,80 @@
+/* -*- 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 "FileSystemEntry.h"
+#include "CallbackRunnables.h"
+#include "FileSystem.h"
+#include "FileSystemDirectoryEntry.h"
+#include "FileSystemFileEntry.h"
+#include "mozilla/dom/FileSystemEntryBinding.h"
+#include "mozilla/dom/UnionTypes.h"
+
+namespace mozilla::dom {
+
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(FileSystemEntry, mParent, mParentEntry,
+                                      mFileSystem)
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(FileSystemEntry)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(FileSystemEntry)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(FileSystemEntry)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+/* static */
+already_AddRefed<FileSystemEntry> FileSystemEntry::Create(
+    nsIGlobalObject* aGlobalObject,
+    const OwningFileOrDirectory& aFileOrDirectory, FileSystem* aFileSystem) {
+  MOZ_ASSERT(aGlobalObject);
+  MOZ_ASSERT(aFileSystem);
+
+  RefPtr<FileSystemEntry> entry;
+  if (aFileOrDirectory.IsFile()) {
+    entry = new FileSystemFileEntry(aGlobalObject, aFileOrDirectory.GetAsFile(),
+                                    nullptr, aFileSystem);
+  } else {
+    MOZ_ASSERT(aFileOrDirectory.IsDirectory());
+    entry = new FileSystemDirectoryEntry(
+        aGlobalObject, aFileOrDirectory.GetAsDirectory(), nullptr, aFileSystem);
+  }
+
+  return entry.forget();
+}
+
+FileSystemEntry::FileSystemEntry(nsIGlobalObject* aGlobal,
+                                 FileSystemEntry* aParentEntry,
+                                 FileSystem* aFileSystem)
+    : mParent(aGlobal), mParentEntry(aParentEntry), mFileSystem(aFileSystem) {
+  MOZ_ASSERT(aGlobal);
+  MOZ_ASSERT(aFileSystem);
+}
+
+FileSystemEntry::~FileSystemEntry() = default;
+
+JSObject* FileSystemEntry::WrapObject(JSContext* aCx,
+                                      JS::Handle<JSObject*> aGivenProto) {
+  return FileSystemEntry_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+void FileSystemEntry::GetParent(
+    const Optional<OwningNonNull<FileSystemEntryCallback>>& aSuccessCallback,
+    const Optional<OwningNonNull<ErrorCallback>>& aErrorCallback) {
+  if (!aSuccessCallback.WasPassed() && !aErrorCallback.WasPassed()) {
+    return;
+  }
+
+  if (mParentEntry) {
+    FileSystemEntryCallbackHelper::Call(GetParentObject(), aSuccessCallback,
+                                        mParentEntry);
+    return;
+  }
+
+  FileSystemEntryCallbackHelper::Call(GetParentObject(), aSuccessCallback,
+                                      this);
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/compat/FileSystemEntry.h b/dom/filesystem/compat/FileSystemEntry.h
new file mode 100644
index 0000000000..2275c600a9
--- /dev/null
+++ b/dom/filesystem/compat/FileSystemEntry.h
@@ -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/. */
+
+#ifndef mozilla_dom_FileSystemEntry_h
+#define mozilla_dom_FileSystemEntry_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/FileSystemBinding.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsIGlobalObject.h"
+#include "nsWrapperCache.h"
+
+namespace mozilla {
+class ErrorResult;
+
+namespace dom {
+
+class FileSystem;
+class OwningFileOrDirectory;
+
+class FileSystemEntry : public nsISupports, public nsWrapperCache {
+ public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(FileSystemEntry)
+
+  static already_AddRefed<FileSystemEntry> Create(
+      nsIGlobalObject* aGlobalObject,
+      const OwningFileOrDirectory& aFileOrDirectory, FileSystem* aFileSystem);
+
+  nsIGlobalObject* GetParentObject() const { return mParent; }
+
+  virtual JSObject* WrapObject(JSContext* aCx,
+                               JS::Handle<JSObject*> aGivenProto) override;
+
+  virtual bool IsFile() const { return false; }
+
+  virtual bool IsDirectory() const { return false; }
+
+  virtual void GetName(nsAString& aName, ErrorResult& aRv) const = 0;
+
+  virtual void GetFullPath(nsAString& aFullPath, ErrorResult& aRv) const = 0;
+
+  void GetParent(
+      const Optional<OwningNonNull<FileSystemEntryCallback>>& aSuccessCallback,
+      const Optional<OwningNonNull<ErrorCallback>>& aErrorCallback);
+
+  FileSystem* Filesystem() const { return mFileSystem; }
+
+ protected:
+  FileSystemEntry(nsIGlobalObject* aGlobalObject, FileSystemEntry* aParentEntry,
+                  FileSystem* aFileSystem);
+  virtual ~FileSystemEntry();
+
+ private:
+  nsCOMPtr<nsIGlobalObject> mParent;
+  RefPtr<FileSystemEntry> mParentEntry;
+  RefPtr<FileSystem> mFileSystem;
+};
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // mozilla_dom_FileSystemEntry_h
diff --git a/dom/filesystem/compat/FileSystemFileEntry.cpp b/dom/filesystem/compat/FileSystemFileEntry.cpp
new file mode 100644
index 0000000000..59216641cc
--- /dev/null
+++ b/dom/filesystem/compat/FileSystemFileEntry.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 "FileSystemFileEntry.h"
+#include "CallbackRunnables.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/dom/FileSystemUtils.h"
+#include "mozilla/dom/MultipartBlobImpl.h"
+#include "mozilla/dom/FileSystemFileEntryBinding.h"
+
+namespace mozilla::dom {
+
+namespace {
+
+class FileCallbackRunnable final : public Runnable {
+ public:
+  FileCallbackRunnable(FileCallback* aCallback, File* aFile)
+      : Runnable("FileCallbackRunnable"), mCallback(aCallback), mFile(aFile) {
+    MOZ_ASSERT(aCallback);
+    MOZ_ASSERT(aFile);
+  }
+
+  // MOZ_CAN_RUN_SCRIPT_BOUNDARY until Runnable::Run is MOZ_CAN_RUN_SCRIPT.  See
+  // bug 1535398.
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY NS_IMETHOD Run() override {
+    // Here we clone the File object.
+
+    RefPtr<File> file = File::Create(mFile->GetParentObject(), mFile->Impl());
+    mCallback->Call(*file);
+    return NS_OK;
+  }
+
+ private:
+  const RefPtr<FileCallback> mCallback;
+  RefPtr<File> mFile;
+};
+
+}  // anonymous namespace
+
+NS_IMPL_CYCLE_COLLECTION_INHERITED(FileSystemFileEntry, FileSystemEntry, mFile)
+
+NS_IMPL_ADDREF_INHERITED(FileSystemFileEntry, FileSystemEntry)
+NS_IMPL_RELEASE_INHERITED(FileSystemFileEntry, FileSystemEntry)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(FileSystemFileEntry)
+NS_INTERFACE_MAP_END_INHERITING(FileSystemEntry)
+
+FileSystemFileEntry::FileSystemFileEntry(nsIGlobalObject* aGlobal, File* aFile,
+                                         FileSystemDirectoryEntry* aParentEntry,
+                                         FileSystem* aFileSystem)
+    : FileSystemEntry(aGlobal, aParentEntry, aFileSystem), mFile(aFile) {
+  MOZ_ASSERT(aGlobal);
+  MOZ_ASSERT(mFile);
+}
+
+FileSystemFileEntry::~FileSystemFileEntry() = default;
+
+JSObject* FileSystemFileEntry::WrapObject(JSContext* aCx,
+                                          JS::Handle<JSObject*> aGivenProto) {
+  return FileSystemFileEntry_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+void FileSystemFileEntry::GetName(nsAString& aName, ErrorResult& aRv) const {
+  mFile->GetName(aName);
+}
+
+void FileSystemFileEntry::GetFullPath(nsAString& aPath,
+                                      ErrorResult& aRv) const {
+  mFile->Impl()->GetDOMPath(aPath);
+  if (aPath.IsEmpty()) {
+    // We're under the root directory. webkitRelativePath
+    // (implemented as GetPath) is for cases when file is selected because its
+    // ancestor directory is selected. But that is not the case here, so need to
+    // manually prepend '/'.
+    nsAutoString name;
+    mFile->GetName(name);
+    aPath.AssignLiteral(FILESYSTEM_DOM_PATH_SEPARATOR_LITERAL);
+    aPath.Append(name);
+  }
+}
+
+void FileSystemFileEntry::GetFile(
+    FileCallback& aSuccessCallback,
+    const Optional<OwningNonNull<ErrorCallback>>& aErrorCallback) const {
+  RefPtr<FileCallbackRunnable> runnable =
+      new FileCallbackRunnable(&aSuccessCallback, mFile);
+
+  FileSystemUtils::DispatchRunnable(GetParentObject(), runnable.forget());
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/compat/FileSystemFileEntry.h b/dom/filesystem/compat/FileSystemFileEntry.h
new file mode 100644
index 0000000000..1fe244a66b
--- /dev/null
+++ b/dom/filesystem/compat/FileSystemFileEntry.h
@@ -0,0 +1,49 @@
+/* -*- 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_FileSystemFileEntry_h
+#define mozilla_dom_FileSystemFileEntry_h
+
+#include "mozilla/dom/FileSystemEntry.h"
+
+namespace mozilla::dom {
+
+class File;
+class FileCallback;
+class FileSystemDirectoryEntry;
+
+class FileSystemFileEntry final : public FileSystemEntry {
+ public:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(FileSystemFileEntry, FileSystemEntry)
+
+  FileSystemFileEntry(nsIGlobalObject* aGlobalObject, File* aFile,
+                      FileSystemDirectoryEntry* aParentEntry,
+                      FileSystem* aFileSystem);
+
+  virtual JSObject* WrapObject(JSContext* aCx,
+                               JS::Handle<JSObject*> aGivenProto) override;
+
+  virtual bool IsFile() const override { return true; }
+
+  virtual void GetName(nsAString& aName, ErrorResult& aRv) const override;
+
+  virtual void GetFullPath(nsAString& aFullPath,
+                           ErrorResult& aRv) const override;
+
+  void GetFile(
+      FileCallback& aSuccessCallback,
+      const Optional<OwningNonNull<ErrorCallback>>& aErrorCallback) const;
+
+ private:
+  ~FileSystemFileEntry();
+
+  RefPtr<File> mFile;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_FileSystemFileEntry_h
diff --git a/dom/filesystem/compat/FileSystemRootDirectoryEntry.cpp b/dom/filesystem/compat/FileSystemRootDirectoryEntry.cpp
new file mode 100644
index 0000000000..fad6243d15
--- /dev/null
+++ b/dom/filesystem/compat/FileSystemRootDirectoryEntry.cpp
@@ -0,0 +1,138 @@
+/* -*- 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 "FileSystemRootDirectoryEntry.h"
+#include "FileSystemRootDirectoryReader.h"
+#include "mozilla/dom/FileSystemUtils.h"
+#include "CallbackRunnables.h"
+#include "nsReadableUtils.h"
+
+namespace mozilla::dom {
+
+NS_IMPL_CYCLE_COLLECTION_INHERITED(FileSystemRootDirectoryEntry,
+                                   FileSystemDirectoryEntry, mEntries)
+
+NS_IMPL_ADDREF_INHERITED(FileSystemRootDirectoryEntry, FileSystemDirectoryEntry)
+NS_IMPL_RELEASE_INHERITED(FileSystemRootDirectoryEntry,
+                          FileSystemDirectoryEntry)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(FileSystemRootDirectoryEntry)
+NS_INTERFACE_MAP_END_INHERITING(FileSystemDirectoryEntry)
+
+FileSystemRootDirectoryEntry::FileSystemRootDirectoryEntry(
+    nsIGlobalObject* aGlobal, Sequence<RefPtr<FileSystemEntry>> aEntries,
+    FileSystem* aFileSystem)
+    : FileSystemDirectoryEntry(aGlobal, nullptr, nullptr, aFileSystem),
+      mEntries(std::move(aEntries)) {
+  MOZ_ASSERT(aGlobal);
+}
+
+FileSystemRootDirectoryEntry::~FileSystemRootDirectoryEntry() = default;
+
+void FileSystemRootDirectoryEntry::GetName(nsAString& aName,
+                                           ErrorResult& aRv) const {
+  aName.Truncate();
+}
+
+void FileSystemRootDirectoryEntry::GetFullPath(nsAString& aPath,
+                                               ErrorResult& aRv) const {
+  aPath.AssignLiteral(FILESYSTEM_DOM_PATH_SEPARATOR_LITERAL);
+}
+
+already_AddRefed<FileSystemDirectoryReader>
+FileSystemRootDirectoryEntry::CreateReader() {
+  RefPtr<FileSystemDirectoryReader> reader =
+      new FileSystemRootDirectoryReader(this, Filesystem(), mEntries);
+  return reader.forget();
+}
+
+void FileSystemRootDirectoryEntry::GetInternal(
+    const nsAString& aPath, const FileSystemFlags& aFlag,
+    const Optional<OwningNonNull<FileSystemEntryCallback>>& aSuccessCallback,
+    const Optional<OwningNonNull<ErrorCallback>>& aErrorCallback,
+    GetInternalType aType) {
+  if (!aSuccessCallback.WasPassed() && !aErrorCallback.WasPassed()) {
+    return;
+  }
+
+  if (aFlag.mCreate) {
+    ErrorCallbackHelper::Call(GetParentObject(), aErrorCallback,
+                              NS_ERROR_DOM_SECURITY_ERR);
+    return;
+  }
+
+  nsTArray<nsString> parts;
+  if (!FileSystemUtils::IsValidRelativeDOMPath(aPath, parts)) {
+    ErrorCallbackHelper::Call(GetParentObject(), aErrorCallback,
+                              NS_ERROR_DOM_NOT_FOUND_ERR);
+    return;
+  }
+
+  MOZ_ASSERT(!parts.IsEmpty());
+
+  RefPtr<FileSystemEntry> entry;
+  for (uint32_t i = 0; i < mEntries.Length(); ++i) {
+    ErrorResult rv;
+    nsAutoString name;
+    mEntries[i]->GetName(name, rv);
+
+    if (NS_WARN_IF(rv.Failed())) {
+      ErrorCallbackHelper::Call(GetParentObject(), aErrorCallback,
+                                rv.StealNSResult());
+      return;
+    }
+
+    if (name == parts[0]) {
+      entry = mEntries[i];
+      break;
+    }
+  }
+
+  // Not found.
+  if (!entry) {
+    ErrorCallbackHelper::Call(GetParentObject(), aErrorCallback,
+                              NS_ERROR_DOM_NOT_FOUND_ERR);
+    return;
+  }
+
+  // No subdirectory in the path.
+  if (parts.Length() == 1) {
+    if ((entry->IsFile() && aType == eGetDirectory) ||
+        (entry->IsDirectory() && aType == eGetFile)) {
+      ErrorCallbackHelper::Call(GetParentObject(), aErrorCallback,
+                                NS_ERROR_DOM_TYPE_MISMATCH_ERR);
+      return;
+    }
+
+    if (aSuccessCallback.WasPassed()) {
+      RefPtr<EntryCallbackRunnable> runnable =
+          new EntryCallbackRunnable(&aSuccessCallback.Value(), entry);
+
+      FileSystemUtils::DispatchRunnable(GetParentObject(), runnable.forget());
+    }
+    return;
+  }
+
+  // Subdirectories, but this is a file.
+  if (entry->IsFile()) {
+    ErrorCallbackHelper::Call(GetParentObject(), aErrorCallback,
+                              NS_ERROR_DOM_NOT_FOUND_ERR);
+    return;
+  }
+
+  // Let's recreate a path without the first directory.
+  nsAutoString path;
+  StringJoinAppend(
+      path,
+      NS_LITERAL_STRING_FROM_CSTRING(FILESYSTEM_DOM_PATH_SEPARATOR_LITERAL),
+      Span{parts}.From(1));
+
+  auto* directoryEntry = static_cast<FileSystemDirectoryEntry*>(entry.get());
+  directoryEntry->GetInternal(path, aFlag, aSuccessCallback, aErrorCallback,
+                              aType);
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/compat/FileSystemRootDirectoryEntry.h b/dom/filesystem/compat/FileSystemRootDirectoryEntry.h
new file mode 100644
index 0000000000..b6ffb976b8
--- /dev/null
+++ b/dom/filesystem/compat/FileSystemRootDirectoryEntry.h
@@ -0,0 +1,48 @@
+/* -*- 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_FileSystemRootDirectoryEntry_h
+#define mozilla_dom_FileSystemRootDirectoryEntry_h
+
+#include "mozilla/dom/FileSystemDirectoryEntry.h"
+
+namespace mozilla::dom {
+
+class FileSystemRootDirectoryEntry final : public FileSystemDirectoryEntry {
+ public:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(FileSystemRootDirectoryEntry,
+                                           FileSystemDirectoryEntry)
+
+  FileSystemRootDirectoryEntry(nsIGlobalObject* aGlobalObject,
+                               Sequence<RefPtr<FileSystemEntry>> aEntries,
+                               FileSystem* aFileSystem);
+
+  virtual void GetName(nsAString& aName, ErrorResult& aRv) const override;
+
+  virtual void GetFullPath(nsAString& aFullPath,
+                           ErrorResult& aRv) const override;
+
+  virtual already_AddRefed<FileSystemDirectoryReader> CreateReader() override;
+
+ private:
+  ~FileSystemRootDirectoryEntry();
+
+  virtual void GetInternal(
+      const nsAString& aPath, const FileSystemFlags& aFlag,
+      const Optional<OwningNonNull<FileSystemEntryCallback>>& aSuccessCallback,
+      const Optional<OwningNonNull<ErrorCallback>>& aErrorCallback,
+      GetInternalType aType) override;
+
+  void Error(const Optional<OwningNonNull<ErrorCallback>>& aErrorCallback,
+             nsresult aError) const;
+
+  Sequence<RefPtr<FileSystemEntry>> mEntries;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_FileSystemRootDirectoryEntry_h
diff --git a/dom/filesystem/compat/FileSystemRootDirectoryReader.cpp b/dom/filesystem/compat/FileSystemRootDirectoryReader.cpp
new file mode 100644
index 0000000000..5d30f0c1cb
--- /dev/null
+++ b/dom/filesystem/compat/FileSystemRootDirectoryReader.cpp
@@ -0,0 +1,93 @@
+/* -*- 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 "FileSystemRootDirectoryReader.h"
+#include "CallbackRunnables.h"
+#include "nsIGlobalObject.h"
+#include "mozilla/dom/FileSystemDirectoryReaderBinding.h"
+#include "mozilla/dom/FileSystemUtils.h"
+
+namespace mozilla::dom {
+
+namespace {
+
+class EntriesCallbackRunnable final : public Runnable {
+ public:
+  EntriesCallbackRunnable(FileSystemEntriesCallback* aCallback,
+                          const Sequence<RefPtr<FileSystemEntry>>& aEntries)
+      : Runnable("EntriesCallbackRunnable"),
+        mCallback(aCallback),
+        mEntries(aEntries) {
+    MOZ_ASSERT(aCallback);
+  }
+
+  // MOZ_CAN_RUN_SCRIPT_BOUNDARY until Runnable::Run is MOZ_CAN_RUN_SCRIPT.  See
+  // bug 1535398.
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY NS_IMETHOD Run() override {
+    Sequence<OwningNonNull<FileSystemEntry>> entries;
+    for (uint32_t i = 0; i < mEntries.Length(); ++i) {
+      if (!entries.AppendElement(mEntries[i].forget(), fallible)) {
+        return NS_ERROR_OUT_OF_MEMORY;
+      }
+    }
+
+    mCallback->Call(entries);
+    return NS_OK;
+  }
+
+ private:
+  const RefPtr<FileSystemEntriesCallback> mCallback;
+  Sequence<RefPtr<FileSystemEntry>> mEntries;
+};
+
+}  // anonymous namespace
+
+NS_IMPL_CYCLE_COLLECTION_INHERITED(FileSystemRootDirectoryReader,
+                                   FileSystemDirectoryReader, mEntries)
+
+NS_IMPL_ADDREF_INHERITED(FileSystemRootDirectoryReader,
+                         FileSystemDirectoryReader)
+NS_IMPL_RELEASE_INHERITED(FileSystemRootDirectoryReader,
+                          FileSystemDirectoryReader)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(FileSystemRootDirectoryReader)
+NS_INTERFACE_MAP_END_INHERITING(FileSystemDirectoryReader)
+
+FileSystemRootDirectoryReader::FileSystemRootDirectoryReader(
+    FileSystemDirectoryEntry* aParentEntry, FileSystem* aFileSystem,
+    const Sequence<RefPtr<FileSystemEntry>>& aEntries)
+    : FileSystemDirectoryReader(aParentEntry, aFileSystem, nullptr),
+      mEntries(aEntries),
+      mAlreadyRead(false) {
+  MOZ_ASSERT(aParentEntry);
+  MOZ_ASSERT(aFileSystem);
+}
+
+FileSystemRootDirectoryReader::~FileSystemRootDirectoryReader() = default;
+
+void FileSystemRootDirectoryReader::ReadEntries(
+    FileSystemEntriesCallback& aSuccessCallback,
+    const Optional<OwningNonNull<ErrorCallback>>& aErrorCallback,
+    ErrorResult& aRv) {
+  if (mAlreadyRead) {
+    RefPtr<EmptyEntriesCallbackRunnable> runnable =
+        new EmptyEntriesCallbackRunnable(&aSuccessCallback);
+
+    aRv =
+        FileSystemUtils::DispatchRunnable(GetParentObject(), runnable.forget());
+    return;
+  }
+
+  // This object can be used only once.
+  mAlreadyRead = true;
+
+  RefPtr<EntriesCallbackRunnable> runnable =
+      new EntriesCallbackRunnable(&aSuccessCallback, mEntries);
+
+  aRv = FileSystemUtils::DispatchRunnable(GetParentObject(), runnable.forget());
+}
+
+}  // namespace mozilla::dom
diff --git a/dom/filesystem/compat/FileSystemRootDirectoryReader.h b/dom/filesystem/compat/FileSystemRootDirectoryReader.h
new file mode 100644
index 0000000000..7429de8a9c
--- /dev/null
+++ b/dom/filesystem/compat/FileSystemRootDirectoryReader.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 mozilla_dom_FileSystemRootDirectoryReader_h
+#define mozilla_dom_FileSystemRootDirectoryReader_h
+
+#include "FileSystemDirectoryReader.h"
+
+namespace mozilla::dom {
+
+class FileSystemRootDirectoryReader final : public FileSystemDirectoryReader {
+ public:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(FileSystemRootDirectoryReader,
+                                           FileSystemDirectoryReader)
+
+  explicit FileSystemRootDirectoryReader(
+      FileSystemDirectoryEntry* aParentEntry, FileSystem* aFileSystem,
+      const Sequence<RefPtr<FileSystemEntry>>& aEntries);
+
+  virtual void ReadEntries(
+      FileSystemEntriesCallback& aSuccessCallback,
+      const Optional<OwningNonNull<ErrorCallback>>& aErrorCallback,
+      ErrorResult& aRv) override;
+
+ private:
+  ~FileSystemRootDirectoryReader();
+
+  Sequence<RefPtr<FileSystemEntry>> mEntries;
+  bool mAlreadyRead;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_FileSystemRootDirectoryReader_h
diff --git a/dom/filesystem/compat/moz.build b/dom/filesystem/compat/moz.build
new file mode 100644
index 0000000000..6757a73d9e
--- /dev/null
+++ b/dom/filesystem/compat/moz.build
@@ -0,0 +1,30 @@
+# -*- 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/.
+
+TEST_DIRS += ["tests"]
+
+EXPORTS.mozilla.dom += [
+    "FileSystem.h",
+    "FileSystemDirectoryEntry.h",
+    "FileSystemDirectoryReader.h",
+    "FileSystemEntry.h",
+    "FileSystemFileEntry.h",
+]
+
+UNIFIED_SOURCES += [
+    "CallbackRunnables.cpp",
+    "FileSystem.cpp",
+    "FileSystemDirectoryEntry.cpp",
+    "FileSystemDirectoryReader.cpp",
+    "FileSystemEntry.cpp",
+    "FileSystemFileEntry.cpp",
+    "FileSystemRootDirectoryEntry.cpp",
+    "FileSystemRootDirectoryReader.cpp",
+]
+
+FINAL_LIBRARY = "xul"
+
+include("/ipc/chromium/chromium-config.mozbuild")
diff --git a/dom/filesystem/compat/tests/mochitest.toml b/dom/filesystem/compat/tests/mochitest.toml
new file mode 100644
index 0000000000..3414a7433a
--- /dev/null
+++ b/dom/filesystem/compat/tests/mochitest.toml
@@ -0,0 +1,11 @@
+[DEFAULT]
+support-files = [
+  "script_entries.js",
+  "!/dom/html/test/form_submit_server.sjs",
+]
+
+["test_basic.html"]
+
+["test_formSubmission.html"]
+
+["test_no_dnd.html"]
diff --git a/dom/filesystem/compat/tests/moz.build b/dom/filesystem/compat/tests/moz.build
new file mode 100644
index 0000000000..2f41008128
--- /dev/null
+++ b/dom/filesystem/compat/tests/moz.build
@@ -0,0 +1,7 @@
+# -*- 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/.
+
+MOCHITEST_MANIFESTS += ["mochitest.toml"]
diff --git a/dom/filesystem/compat/tests/script_entries.js b/dom/filesystem/compat/tests/script_entries.js
new file mode 100644
index 0000000000..7f52fe6bf2
--- /dev/null
+++ b/dom/filesystem/compat/tests/script_entries.js
@@ -0,0 +1,47 @@
+/* eslint-env mozilla/chrome-script */
+// eslint-disable-next-line mozilla/reject-importGlobalProperties
+Cu.importGlobalProperties(["File", "Directory"]);
+var tmpFile, tmpDir;
+
+addMessageListener("entries.open", function (e) {
+  tmpFile = Services.dirsvc
+    .QueryInterface(Ci.nsIProperties)
+    .get("TmpD", Ci.nsIFile);
+  tmpFile.append("file.txt");
+  tmpFile.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, 0o600);
+
+  tmpDir = Services.dirsvc
+    .QueryInterface(Ci.nsIProperties)
+    .get("TmpD", Ci.nsIFile);
+
+  tmpDir.append("dir-test");
+  tmpDir.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0o700);
+
+  var file1 = tmpDir.clone();
+  file1.append("foo.txt");
+  file1.create(Ci.nsIFile.NORMAL_FILE_TYPE, 0o600);
+
+  var dir1 = tmpDir.clone();
+  dir1.append("subdir");
+  dir1.create(Ci.nsIFile.DIRECTORY_TYPE, 0o700);
+
+  var file2 = dir1.clone();
+  file2.append("bar..txt"); // Note the double ..
+  file2.create(Ci.nsIFile.NORMAL_FILE_TYPE, 0o600);
+
+  var dir2 = dir1.clone();
+  dir2.append("subsubdir");
+  dir2.create(Ci.nsIFile.DIRECTORY_TYPE, 0o700);
+
+  File.createFromNsIFile(tmpFile).then(function (file) {
+    sendAsyncMessage("entries.opened", {
+      data: [new Directory(tmpDir.path), file],
+    });
+  });
+});
+
+addMessageListener("entries.delete", function (e) {
+  tmpFile.remove(true);
+  tmpDir.remove(true);
+  sendAsyncMessage("entries.deleted");
+});
diff --git a/dom/filesystem/compat/tests/test_basic.html b/dom/filesystem/compat/tests/test_basic.html
new file mode 100644
index 0000000000..4ad0c37d67
--- /dev/null
+++ b/dom/filesystem/compat/tests/test_basic.html
@@ -0,0 +1,549 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for Blink FileSystem API - subset</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+
+<body>
+<input id="entries" type="file"></input>
+<script type="application/javascript">
+var fileEntry;
+var directoryEntry;
+var script;
+
+function setup_tests() {
+  SpecialPowers.pushPrefEnv({"set": [["dom.webkitBlink.dirPicker.enabled", true],
+                                     ["dom.filesystem.pathcheck.disabled", true],
+                                     ["dom.webkitBlink.filesystem.enabled", true]]}, next);
+}
+
+function populate_entries() {
+  var url = SimpleTest.getTestFileURL("script_entries.js");
+  script = SpecialPowers.loadChromeScript(url);
+
+  function onOpened(message) {
+    var entries = document.getElementById("entries");
+    SpecialPowers.wrap(entries).mozSetDndFilesAndDirectories(message.data);
+    next();
+  }
+
+  script.addMessageListener("entries.opened", onOpened);
+  script.sendAsyncMessage("entries.open");
+}
+
+function test_entries() {
+  var entries = document.getElementById("entries");
+  ok("webkitEntries" in entries, "HTMLInputElement.webkitEntries");
+  is(entries.webkitEntries.length, 2, "HTMLInputElement.webkitEntries.length == 2");
+  is(entries.files.length, 1, "HTMLInputElement.files is still populated");
+
+  for (var i = 0; i < entries.webkitEntries.length; ++i) {
+    if (entries.webkitEntries[i].isFile) {
+      ok(!fileEntry, "We just want 1 fileEntry");
+      fileEntry = entries.webkitEntries[i];
+    } else {
+      ok(entries.webkitEntries[i].isDirectory, "If not a file, we have a directory.");
+      ok(!directoryEntry, "We just want 1 directoryEntry");
+      directoryEntry = entries.webkitEntries[i];
+    }
+  }
+
+  next();
+}
+
+function test_fileEntry() {
+  ok("name" in fileEntry, "We have a name.");
+  ok("fullPath" in fileEntry, "We have a fullPath.");
+  ok("filesystem" in fileEntry, "We have a filesystem.");
+
+  next();
+}
+
+function test_fileEntry_file() {
+  fileEntry.file(function(file) {
+    ok(file, "We have a file here!");
+    is(file.name, fileEntry.name, "Same file name.");
+    next();
+  }, function() {
+    ok(false, "Something when wrong!");
+  });
+}
+
+function test_fileEntry_getParent() {
+  fileEntry.getParent(function(entry) {
+    is(fileEntry.fullPath, entry.fullPath, "Top level FileEntry should return itself as parent.");
+    next();
+  }, function() {
+    ok(false, "This is wrong.");
+  });
+}
+
+function test_directoryEntry() {
+  ok("name" in directoryEntry, "We have a name.");
+  ok("fullPath" in directoryEntry, "We have a fullPath.");
+  ok("filesystem" in directoryEntry, "We have a filesystem.");
+
+  next();
+}
+
+function test_directoryEntry_createReader() {
+  var reader = directoryEntry.createReader();
+  ok(reader, "We have a DirectoryReader");
+
+  reader.readEntries(function(a) {
+    ok(Array.isArray(a), "We want an array.");
+    is(a.length, 2, "reader.readyEntries returns 2 elements.");
+
+    for (var i = 0; i < 2; ++i) {
+      ok(a[i].name == "subdir" || a[i].name == "foo.txt", "Correct names");
+      is(a[i].fullPath, directoryEntry.fullPath + "/" + a[i].name, "FullPath is correct");
+    }
+
+    // Called twice:
+    reader.readEntries(function(a1) {
+      ok(Array.isArray(a1), "We want an array.");
+      is(a1.length, 0, "reader.readyEntries returns 0 elements.");
+      next();
+    }, function() {
+      ok(false, "Something when wrong!");
+    });
+  }, function() {
+    ok(false, "Something when wrong!");
+  });
+}
+
+function test_directoryEntry_getParent() {
+  directoryEntry.getParent(function(entry) {
+    is(directoryEntry.fullPath, entry.fullPath, "Top level FileEntry should return itself as parent.");
+    next();
+  }, function() {
+    ok(false, "This is wrong.");
+  });
+}
+
+function test_directoryEntry_getFile_securityError() {
+  directoryEntry.getFile("foo", { create: true },
+  function() {
+    ok(false, "This should not happen.");
+  }, function(e) {
+    is(e.name, "SecurityError", "This must generate a SecurityError.");
+    next();
+  });
+}
+
+function test_directoryEntry_getFile_typeMismatchError() {
+  directoryEntry.getFile("subdir", {},
+  function() {
+    ok(false, "This should not happen.");
+  }, function(e) {
+    is(e.name, "TypeMismatchError", "This must generate a TypeMismatchError.");
+    next();
+  });
+}
+
+function test_directoryEntry_getFile_nonValidPath() {
+  directoryEntry.getFile("../../", {},
+  function() {
+    ok(false, "This should not happen.");
+  }, function(e) {
+    is(e.name, "NotFoundError", "This must generate a NotFoundError.");
+    next();
+  });
+}
+
+function test_directoryEntry_getFile_nonExistingPath() {
+  directoryEntry.getFile("foo_bar.txt", {},
+  function() {
+    ok(false, "This should not happen.");
+  }, function(e) {
+    is(e.name, "NotFoundError", "This must generate a NotFoundError.");
+    next();
+  });
+}
+
+function test_directoryEntry_getFile_simple() {
+  directoryEntry.getFile("foo.txt", {},
+  function(e) {
+    is(e.name, "foo.txt", "We have the right FileEntry.");
+    test_getParent(e, directoryEntry, /* nested */ false);
+  }, function(e) {
+    ok(false, "This should not happen.");
+  });
+}
+
+function test_directoryEntry_getFile_deep() {
+  directoryEntry.getFile("subdir/bar..txt", {},
+  function(e) {
+    is(e.name, "bar..txt", "We have the right FileEntry.");
+    test_getParent(e, directoryEntry, /* nested */ true);
+  }, function(e) {
+    ok(false, "This should not happen.");
+  });
+}
+
+function test_directoryEntry_getDirectory_securityError() {
+  directoryEntry.getDirectory("foo", { create: true },
+  function() {
+    ok(false, "This should not happen.");
+  }, function(e) {
+    is(e.name, "SecurityError", "This must generate a SecurityError.");
+    next();
+  });
+}
+
+function test_directoryEntry_getDirectory_typeMismatchError() {
+  directoryEntry.getDirectory("foo.txt", {},
+  function() {
+    ok(false, "This should not happen.");
+  }, function(e) {
+    is(e.name, "TypeMismatchError", "This must generate a TypeMismatchError.");
+    next();
+  });
+}
+
+function test_directoryEntry_getDirectory_nonValidPath() {
+  directoryEntry.getDirectory("../../", {},
+  function() {
+    ok(false, "This should not happen.");
+  }, function(e) {
+    is(e.name, "NotFoundError", "This must generate a NotFoundError.");
+    next();
+  });
+}
+
+function test_directoryEntry_getDirectory_nonExistingPath() {
+  directoryEntry.getDirectory("non_existing_dir", {},
+  function() {
+    ok(false, "This should not happen.");
+  }, function(e) {
+    is(e.name, "NotFoundError", "This must generate a NotFoundError.");
+    next();
+  });
+}
+
+function test_directoryEntry_getDirectory_simple() {
+  directoryEntry.getDirectory("subdir", {},
+  function(e) {
+    is(e.name, "subdir", "We have the right DirectoryEntry.");
+    test_getParent(e, directoryEntry, /* nested */ false);
+  }, function(e) {
+    ok(false, "This should not happen.");
+  });
+}
+
+function test_directoryEntry_getDirectory_deep() {
+  directoryEntry.getDirectory("subdir/subsubdir", {},
+  function(e) {
+    is(e.name, "subsubdir", "We have the right DirectoryEntry.");
+    test_getParent(e, directoryEntry, /* nested */ true);
+  }, function(e) {
+    ok(false, "This should not happen.");
+  });
+}
+
+function test_filesystem() {
+  is(fileEntry.filesystem, directoryEntry.filesystem, "FileSystem object is shared.");
+
+  var fs = fileEntry.filesystem;
+  ok(fs.name, "FileSystem.name exists.");
+  ok(fs.root, "FileSystem has a root.");
+
+  is(fs.root.name, "", "FileSystem.root.name must be an empty string.");
+  is(fs.root.fullPath, "/", "FileSystem.root.fullPath must be '/'");
+
+  var reader = fs.root.createReader();
+  reader.readEntries(function(a) {
+    ok(Array.isArray(a), "We want an array.");
+    is(a.length, 2, "reader.readyEntries returns 2 elements.");
+    next();
+  }, function() {
+    ok(false, "Something when wrong!");
+  });
+}
+
+function test_root_getFile_securityError() {
+  fileEntry.filesystem.root.getFile("foo", { create: true },
+  function() {
+    ok(false, "This should not happen.");
+  }, function(e) {
+    is(e.name, "SecurityError", "This must generate a SecurityError.");
+    next();
+  });
+}
+
+function test_root_getFile_typeMismatchError() {
+  fileEntry.filesystem.root.getFile(directoryEntry.name, {},
+  function() {
+    ok(false, "This should not happen.");
+  }, function(e) {
+    is(e.name, "TypeMismatchError", "This must generate a TypeMismatchError.");
+    next();
+  });
+}
+
+function test_root_getFile_nonValidPath() {
+  fileEntry.filesystem.root.getFile("../../", {},
+  function() {
+    ok(false, "This should not happen.");
+  }, function(e) {
+    is(e.name, "NotFoundError", "This must generate a NotFoundError.");
+    next();
+  });
+}
+
+function test_root_getFile_nonExistingPath() {
+  fileEntry.filesystem.root.getFile("existing.txt", {},
+  function() {
+    ok(false, "This should not happen.");
+  }, function(e) {
+    is(e.name, "NotFoundError", "This must generate a NotFoundError.");
+    next();
+  });
+}
+
+function test_root_getFile_simple() {
+  fileEntry.filesystem.root.getFile(fileEntry.name, {},
+  function(e) {
+    is(e.name, fileEntry.name, "We have the right FileEntry.");
+    next();
+  }, function(e) {
+    ok(false, "This should not happen.");
+  });
+}
+
+function test_root_getFile_deep() {
+  fileEntry.filesystem.root.getFile(directoryEntry.name + "/subdir/bar..txt", {},
+  function(e) {
+    is(e.name, "bar..txt", "We have the right FileEntry.");
+    next();
+  }, function(e) {
+    ok(false, "This should not happen.");
+  });
+}
+
+function test_root_getDirectory_securityError() {
+  fileEntry.filesystem.root.getDirectory("foo", { create: true },
+  function() {
+    ok(false, "This should not happen.");
+  }, function(e) {
+    is(e.name, "SecurityError", "This must generate a SecurityError.");
+    next();
+  });
+}
+
+function test_root_getDirectory_typeMismatchError() {
+  fileEntry.filesystem.root.getDirectory(fileEntry.name, {},
+  function() {
+    ok(false, "This should not happen.");
+  }, function(e) {
+    is(e.name, "TypeMismatchError", "This must generate a TypeMismatchError.");
+    next();
+  });
+}
+
+function test_root_getDirectory_nonValidPath() {
+  fileEntry.filesystem.root.getDirectory("../../", {},
+  function() {
+    ok(false, "This should not happen.");
+  }, function(e) {
+    is(e.name, "NotFoundError", "This must generate a NotFoundError.");
+    next();
+  });
+}
+
+function test_root_getDirectory_nonExistingPath() {
+  fileEntry.filesystem.root.getDirectory("404", {},
+  function() {
+    ok(false, "This should not happen.");
+  }, function(e) {
+    is(e.name, "NotFoundError", "This must generate a NotFoundError.");
+    next();
+  });
+}
+
+function test_root_getDirectory_simple() {
+  fileEntry.filesystem.root.getDirectory(directoryEntry.name, {},
+  function(e) {
+    is(e.name, directoryEntry.name, "We have the right DirectoryEntry.");
+    next();
+  }, function(e) {
+    ok(false, "This should not happen.");
+  });
+}
+
+function test_root_getDirectory_deep() {
+  fileEntry.filesystem.root.getDirectory(directoryEntry.name + "/subdir/subsubdir", {},
+  function(e) {
+    is(e.name, "subsubdir", "We have the right DirectoryEntry.");
+    next();
+  }, function(e) {
+    ok(false, "This should not happen.");
+  });
+}
+
+function cleanUpTestingFiles() {
+  script.addMessageListener("entries.deleted", function onDeleted() {
+    script.removeMessageListener("entries.deleted");
+    script.destroy();
+    next();
+  });
+
+  script.sendAsyncMessage("entries.delete");
+}
+
+function test_getParent(entry, parentEntry, nested) {
+  entry.getParent(function(e) {
+    ok(e, "We have a parent Entry.");
+    if (!nested) {
+      is(e, parentEntry, "Parent entry matches");
+      next();
+    } else {
+      test_getParent(e, parentEntry, false);
+    }
+  }, function(e) {
+    ok(false, "This should not happen.");
+  });
+}
+
+function test_webkitRelativePath() {
+  fileEntry.file(function(file1) {
+    ok(file1, "We have a file here!");
+    ok(!file1.webkitRelativePath, "webkitRelativePath is an empty string");
+
+    fileEntry.file(function(file2) {
+      ok(file2, "We have a file here!");
+      ok(!file2.webkitRelativePath, "webkitRelativePath is an empty string");
+      isnot(file1, file2, "The 2 files are not the same");
+
+      next();
+    }, function() {
+      ok(false, "Something when wrong!");
+    });
+  }, function() {
+    ok(false, "Something when wrong!");
+  });
+}
+
+function test_deprecatedCallbacks() {
+  try {
+    fileEntry.file({ handleEvent: _ => { ok(false, "This function should not be called!"); }});
+    ok(false, "fileEntry.file() should throw with wrong arguments");
+  } catch (e) {
+    ok(true, "fileEntry.file() should throw with wrong arguments");
+    is(e.name, "TypeError", "Correct exception");
+  }
+
+  try {
+    fileEntry.getParent({ handleEvent: _ => { ok(false, "This function should not be called!"); }});
+    ok(false, "fileEntry.getParent() should throw with wrong arguments");
+  } catch (e) {
+    ok(true, "fileEntry.getParent() should throw with wrong arguments");
+    is(e.name, "TypeError", "Correct exception");
+  }
+
+  try {
+    directoryEntry.getFile("file.txt", {}, { handleEvent: _ => { ok(false, "This function should not be called!"); }});
+    ok(false, "directoryEntry.getFile() should throw with wrong arguments");
+  } catch (e) {
+    ok(true, "directoryEntry.getFile() should throw with wrong arguments");
+    is(e.name, "TypeError", "Correct exception");
+  }
+
+  try {
+    directoryEntry.getDirectory("foo", { create: true }, { handleEvent: _ => { ok(false, "This function should not be called!"); }});
+    ok(false, "directoryEntry.getDirectory() should throw with wrong arguments");
+  } catch (e) {
+    ok(true, "directoryEntry.getDirectory() should throw with wrong arguments");
+    is(e.name, "TypeError", "Correct exception");
+  }
+
+  try {
+    directoryEntry.getParent({ handleEvent: _ => { ok(false, "This function should not be called!"); }});
+    ok(false, "directoryEntry.getParent() should throw with wrong arguments");
+  } catch (e) {
+    ok(true, "directoryEntry.getParent() should throw with wrong arguments");
+    is(e.name, "TypeError", "Correct exception");
+  }
+
+  let reader = directoryEntry.createReader();
+  ok(reader, "We have a DirectoryReader");
+
+  try {
+    reader.readEntries({ handleEvent: _ => { ok(false, "This function should not be called!"); }});
+    ok(false, "reader.readEntries() should throw with wrong arguments");
+  } catch (e) {
+    ok(true, "reader.readEntries() should throw with wrong arguments");
+    is(e.name, "TypeError", "Correct exception");
+  }
+
+  next();
+}
+
+var tests = [
+  setup_tests,
+  populate_entries,
+
+  test_entries,
+
+  test_fileEntry,
+  test_fileEntry_file,
+  test_fileEntry_getParent,
+
+  test_directoryEntry,
+  test_directoryEntry_createReader,
+  test_directoryEntry_getParent,
+
+  test_directoryEntry_getFile_securityError,
+  test_directoryEntry_getFile_typeMismatchError,
+  test_directoryEntry_getFile_nonValidPath,
+  test_directoryEntry_getFile_nonExistingPath,
+  test_directoryEntry_getFile_simple,
+  test_directoryEntry_getFile_deep,
+
+  test_directoryEntry_getDirectory_securityError,
+  test_directoryEntry_getDirectory_typeMismatchError,
+  test_directoryEntry_getDirectory_nonValidPath,
+  test_directoryEntry_getDirectory_nonExistingPath,
+  test_directoryEntry_getDirectory_simple,
+  test_directoryEntry_getDirectory_deep,
+
+  test_filesystem,
+
+  test_root_getFile_securityError,
+  test_root_getFile_typeMismatchError,
+  test_root_getFile_nonValidPath,
+  test_root_getFile_nonExistingPath,
+  test_root_getFile_simple,
+  test_root_getFile_deep,
+
+  test_root_getDirectory_securityError,
+  test_root_getDirectory_typeMismatchError,
+  test_root_getDirectory_nonValidPath,
+  test_root_getDirectory_nonExistingPath,
+  test_root_getDirectory_simple,
+  test_root_getDirectory_deep,
+
+  test_webkitRelativePath,
+
+  test_deprecatedCallbacks,
+
+  cleanUpTestingFiles,
+];
+
+function next() {
+  if (!tests.length) {
+    SimpleTest.finish();
+    return;
+  }
+
+  var test = tests.shift();
+  test();
+}
+
+SimpleTest.waitForExplicitFinish();
+next();
+</script>
+</body>
+</html>
diff --git a/dom/filesystem/compat/tests/test_formSubmission.html b/dom/filesystem/compat/tests/test_formSubmission.html
new file mode 100644
index 0000000000..2447e7a071
--- /dev/null
+++ b/dom/filesystem/compat/tests/test_formSubmission.html
@@ -0,0 +1,271 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for Directory form submission</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+  <meta http-equiv="Content-Type" content="text/html;charset=utf-8">
+</head>
+<body onload="return next();">
+
+<iframe name="target_iframe" id="target_iframe"></iframe>
+
+<form action="../../../html/test/form_submit_server.sjs" target="target_iframe" id="form"
+      method="POST" enctype="multipart/form-data">
+</form>
+
+<script class="testbody" type="text/javascript">
+var form;
+var iframe;
+var input;
+var script;
+var xhr;
+
+function setup_tests() {
+  form = document.getElementById("form");
+
+  iframe = document.getElementById("target_iframe");
+  iframe.onload = function() {
+    info("Frame loaded!");
+    next();
+  };
+
+  SpecialPowers.pushPrefEnv({"set": [["dom.webkitBlink.dirPicker.enabled", true],
+                                     ["dom.filesystem.pathcheck.disabled", true],
+                                     ["dom.webkitBlink.filesystem.enabled", true]]}, next);
+}
+
+function populate_entries(webkitDirectory) {
+  var url = SimpleTest.getTestFileURL("script_entries.js");
+  script = SpecialPowers.loadChromeScript(url);
+
+  if (input) {
+    form.removeChild(input);
+  }
+
+  input = document.createElement("input");
+  input.setAttribute("id", "input");
+  input.setAttribute("type", "file");
+  input.setAttribute("name", "input");
+
+  if (webkitDirectory) {
+    input.setAttribute("webkitdirectory", "true");
+  }
+
+  form.appendChild(input);
+
+  function onOpened(message) {
+    input.addEventListener("change", function() {
+      next();
+    }, {once: true});
+
+    SpecialPowers.wrap(input).mozSetDndFilesAndDirectories([message.data[0]]);
+  }
+
+  script.addMessageListener("entries.opened", onOpened);
+  script.sendAsyncMessage("entries.open");
+}
+
+function delete_entries() {
+  script.sendAsyncMessage("entries.delete");
+  script.addMessageListener("entries.deleted", function() {
+    script.destroy();
+    next();
+  });
+}
+
+function setup_plain() {
+  info("Preparing for a plain text submission...");
+  form.action = "../../../html/test/form_submit_server.sjs?plain";
+  form.method = "POST";
+  form.enctype = "text/plain";
+  form.submit();
+}
+
+function test_plain() {
+  var content = iframe.contentDocument.documentElement.textContent;
+  var submission = JSON.parse(content);
+  info(submission);
+  is(submission, input.webkitEntries.map(function(v) {
+     return "input=" + v.name + "\r\n";
+  }).join(""), "Data match");
+
+  next();
+}
+
+function setup_urlencoded() {
+  info("Preparing for a urlencoded submission...");
+  form.action = "../../../html/test/form_submit_server.sjs?url";
+  form.method = "POST";
+  form.enctype = "application/x-www-form-urlencoded";
+  form.submit();
+}
+
+function setup_urlencoded_get() {
+  info("Preparing for a urlencoded+GET submission...");
+  form.action = "../../../html/test/form_submit_server.sjs?xxyy";
+  form.method = "GET";
+  form.enctype = "";
+  form.submit();
+}
+
+function setup_urlencoded_empty() {
+  info("Preparing for a urlencoded+default values submission...");
+  form.action = "../../../html/test/form_submit_server.sjs";
+  form.method = "";
+  form.enctype = "";
+  form.submit();
+}
+
+function test_urlencoded() {
+  var content = iframe.contentDocument.documentElement.textContent;
+  var submission = JSON.parse(content);
+  info(submission);
+  is(submission, input.webkitEntries.map(function(v) {
+     return "input=" + v.name;
+  }).join("&"), "Data match");
+
+  next();
+}
+
+function setup_formData() {
+  info("Preparing for a fromData submission...");
+
+  xhr = new XMLHttpRequest();
+  xhr.onload = next;
+  xhr.open("POST", "../../../html/test/form_submit_server.sjs");
+  xhr.send(new FormData(form));
+}
+
+function test_multipart() {
+  var submission = JSON.parse(xhr.responseText);
+
+  var array = input.webkitEntries;
+  is(submission.length, array.length, "Same length");
+  info(submission);
+
+  for (var i = 0; i < array.length; ++i) {
+    if (array[i].isDirectory) {
+      is(submission[i].headers["Content-Disposition"],
+         "form-data; name=\"input\"; filename=\"/" + array[i].name + "\"",
+         "Correct Content-Disposition");
+      is(submission[i].headers["Content-Type"], "application/octet-stream",
+         "Correct Content-Type");
+      is(submission[i].body, "", "Correct body");
+    } else {
+      ok(array[i].isFile);
+      is(submission[i].headers["Content-Disposition"],
+         "form-data; name=\"input\"; filename=\"" + array[i].name + "\"",
+         "Correct Content-Disposition");
+      is(submission[i].headers["Content-Type"], array[i].type,
+         "Correct Content-Type");
+      is(submission[i].body, "", "Correct body");
+    }
+  }
+
+  next();
+}
+
+function getInputFiles(inputElement) {
+  var array = [];
+  for (var i = 0; i < inputElement.files.length; ++i) {
+    array.push(inputElement.files[i]);
+  }
+  return array;
+}
+
+function test_webkit_plain() {
+  var content = iframe.contentDocument.documentElement.textContent;
+  var submission = JSON.parse(content);
+
+  is(submission, getInputFiles(input).map(function(v) {
+    return "input=" + v.name + "\r\n";
+  }).join(""), "Data match");
+
+  next();
+}
+
+function test_webkit_urlencoded() {
+  var content = iframe.contentDocument.documentElement.textContent;
+  var submission = JSON.parse(content);
+  is(submission, getInputFiles(input).map(function(v) {
+     return "input=" + v.name;
+  }).join("&"), "Data match");
+
+  next();
+}
+
+function test_webkit_multipart() {
+  var submission = JSON.parse(xhr.responseText);
+  var array = getInputFiles(input);
+  is(submission.length, array.length, "Same length");
+
+  for (var i = 0; i < array.length; ++i) {
+    ok(array[i] instanceof File);
+    is(submission[i].headers["Content-Disposition"],
+       "form-data; name=\"input\"; filename=\"" + array[i].webkitRelativePath + "\"",
+       "Correct Content-Disposition");
+    is(submission[i].headers["Content-Type"], array[i].type,
+       "Correct Content-Type");
+    is(submission[i].body, "", "Correct body");
+  }
+  next();
+}
+
+var tests = [
+  setup_tests,
+
+  function() { populate_entries(false); },
+
+  setup_plain,
+  test_plain,
+
+  setup_urlencoded,
+  test_urlencoded,
+
+  setup_urlencoded_get,
+  test_urlencoded,
+
+  setup_urlencoded_empty,
+  test_urlencoded,
+
+  setup_formData,
+  test_multipart,
+
+  delete_entries,
+
+  function() { populate_entries(true); },
+
+  setup_plain,
+  test_webkit_plain,
+
+  setup_urlencoded,
+  test_webkit_urlencoded,
+
+  setup_urlencoded_get,
+  test_webkit_urlencoded,
+
+  setup_urlencoded_empty,
+  test_webkit_urlencoded,
+
+  setup_formData,
+  test_webkit_multipart,
+
+  delete_entries,
+];
+
+function next() {
+  if (!tests.length) {
+    SimpleTest.finish();
+    return;
+  }
+
+  var test = tests.shift();
+  test();
+}
+
+SimpleTest.waitForExplicitFinish();
+
+</script>
+</body>
+</html>
diff --git a/dom/filesystem/compat/tests/test_no_dnd.html b/dom/filesystem/compat/tests/test_no_dnd.html
new file mode 100644
index 0000000000..c49dd5d40f
--- /dev/null
+++ b/dom/filesystem/compat/tests/test_no_dnd.html
@@ -0,0 +1,84 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for Blink FileSystem API - no DND == no webkitEntries</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+
+<body>
+<script type="application/javascript">
+var fileEntry;
+var directoryEntry;
+var script;
+var entries;
+
+function setup_tests() {
+  SpecialPowers.pushPrefEnv({"set": [["dom.webkitBlink.dirPicker.enabled", true],
+                                     ["dom.filesystem.pathcheck.disabled", true],
+                                     ["dom.webkitBlink.filesystem.enabled", true]]}, next);
+}
+
+function populate_entries() {
+  entries = document.createElement("input");
+  entries.setAttribute("type", "file");
+  document.body.appendChild(entries);
+
+  var url = SimpleTest.getTestFileURL("script_entries.js");
+  script = SpecialPowers.loadChromeScript(url);
+
+  function onOpened(message) {
+    for (var i = 0 ; i < message.data.length; ++i) {
+      if (message.data[i] instanceof File) {
+        SpecialPowers.wrap(entries).mozSetFileArray([message.data[i]]);
+        next();
+      }
+    }
+  }
+
+  script.addMessageListener("entries.opened", onOpened);
+  script.sendAsyncMessage("entries.open");
+}
+
+function test_entries() {
+  ok("webkitEntries" in entries, "HTMLInputElement.webkitEntries");
+  is(entries.webkitEntries.length, 0, "HTMLInputElement.webkitEntries.length == 0");
+  is(entries.files.length, 1, "HTMLInputElement.files is still populated");
+
+  next();
+}
+
+function cleanUpTestingFiles() {
+  script.addMessageListener("entries.deleted", function onDeleted() {
+    script.removeMessageListener("entries.deleted");
+    script.destroy();
+    next();
+  });
+
+  script.sendAsyncMessage("entries.delete");
+}
+
+var tests = [
+  setup_tests,
+  populate_entries,
+
+  test_entries,
+
+  cleanUpTestingFiles,
+];
+
+function next() {
+  if (!tests.length) {
+    SimpleTest.finish();
+    return;
+  }
+
+  var test = tests.shift();
+  test();
+}
+
+SimpleTest.waitForExplicitFinish();
+next();
+</script>
+</body>
+</html>
diff --git a/dom/filesystem/moz.build b/dom/filesystem/moz.build
new file mode 100644
index 0000000000..8287f85777
--- /dev/null
+++ b/dom/filesystem/moz.build
@@ -0,0 +1,50 @@
+# -*- 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 += ["compat"]
+
+TEST_DIRS += ["tests"]
+
+EXPORTS.mozilla.dom += [
+    "Directory.h",
+    "FileSystemBase.h",
+    "FileSystemRequestParent.h",
+    "FileSystemSecurity.h",
+    "FileSystemTaskBase.h",
+    "FileSystemUtils.h",
+    "GetFilesHelper.h",
+    "OSFileSystem.h",
+]
+
+UNIFIED_SOURCES += [
+    "Directory.cpp",
+    "FileSystemBase.cpp",
+    "FileSystemRequestParent.cpp",
+    "FileSystemSecurity.cpp",
+    "FileSystemTaskBase.cpp",
+    "FileSystemUtils.cpp",
+    "GetDirectoryListingTask.cpp",
+    "GetFileOrDirectoryTask.cpp",
+    "GetFilesHelper.cpp",
+    "GetFilesTask.cpp",
+    "OSFileSystem.cpp",
+]
+
+FINAL_LIBRARY = "xul"
+
+IPDL_SOURCES += [
+    "PFileSystemParams.ipdlh",
+    "PFileSystemRequest.ipdl",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+LOCAL_INCLUDES += [
+    "/dom/base",
+]
diff --git a/dom/filesystem/tests/filesystem_commons.js b/dom/filesystem/tests/filesystem_commons.js
new file mode 100644
index 0000000000..af0ce36339
--- /dev/null
+++ b/dom/filesystem/tests/filesystem_commons.js
@@ -0,0 +1,180 @@
+function createPath(parentDir, dirOrFile) {
+  return parentDir.path + (parentDir.path == "/" ? "" : "/") + dirOrFile.name;
+}
+
+function createRelativePath(parentDir, dirOrFile) {
+  let path = createPath(parentDir, dirOrFile);
+  is(path[0], "/", "The full path should start with '/'");
+  return path.substring(1);
+}
+
+function setup_tests(aNext) {
+  SimpleTest.requestLongerTimeout(2);
+  SpecialPowers.pushPrefEnv(
+    {
+      set: [
+        ["dom.filesystem.pathcheck.disabled", true],
+        ["dom.webkitBlink.dirPicker.enabled", true],
+      ],
+    },
+    aNext
+  );
+}
+
+function test_basic(aDirectory, aNext) {
+  ok(aDirectory, "Directory exists.");
+  ok(aDirectory instanceof Directory, "We have a directory.");
+  is(aDirectory.path, "/" + aDirectory.name, "directory.path must be '/'+name");
+  aNext();
+}
+
+function test_getFilesAndDirectories(aDirectory, aRecursive, aNext) {
+  function checkSubDir(dir) {
+    return dir.getFilesAndDirectories().then(function (data) {
+      for (var i = 0; i < data.length; ++i) {
+        ok(
+          data[i] instanceof File || data[i] instanceof Directory,
+          "Just Files or Directories"
+        );
+        if (data[i] instanceof Directory) {
+          isnot(
+            data[i].name,
+            "/",
+            "Subdirectory should be called with the leafname"
+          );
+          isnot(
+            data[i].path,
+            "/",
+            "Subdirectory path should be called with the leafname"
+          );
+          isnot(
+            data[i].path,
+            dir.path,
+            "Subdirectory path should contain the parent path."
+          );
+          is(
+            data[i].path,
+            createPath(dir, data[i]),
+            "Subdirectory path should be called parentdir.path + '/' + leafname: " +
+              data[i].path
+          );
+        }
+
+        if (data[i] instanceof File) {
+          is(
+            data[i].webkitRelativePath,
+            createRelativePath(dir, data[i]),
+            "File.webkitRelativePath should be called: parentdir.path + '/' + file.name: " +
+              data[i].webkitRelativePath
+          );
+          ok(
+            !data[i].webkitRelativePath.endsWith("symlink.txt"),
+            "We should never see a path ending with symlink.txt, our symlink sentinel."
+          );
+        }
+      }
+    });
+  }
+
+  aDirectory
+    .getFilesAndDirectories()
+    .then(
+      function (data) {
+        ok(data.length, "We should have some data.");
+        var promises = [];
+        for (var i = 0; i < data.length; ++i) {
+          ok(
+            data[i] instanceof File || data[i] instanceof Directory,
+            "Just Files or Directories: " + data[i].name
+          );
+          if (data[i] instanceof Directory) {
+            isnot(
+              data[i].name,
+              "/",
+              "Subdirectory should be called with the leafname"
+            );
+            is(
+              data[i].path,
+              createPath(aDirectory, data[i]),
+              "Subdirectory path should be called parentdir.path + '/' + leafname: " +
+                data[i].path
+            );
+            if (aRecursive) {
+              promises.push(checkSubDir(data[i]));
+            }
+          }
+
+          if (data[i] instanceof File) {
+            is(
+              data[i].webkitRelativePath,
+              createRelativePath(aDirectory, data[i]),
+              "File.webkitRelativePath should be called file.name: " +
+                data[i].webkitRelativePath
+            );
+          }
+        }
+
+        return Promise.all(promises);
+      },
+      function () {
+        ok(false, "Something when wrong");
+      }
+    )
+    .then(aNext);
+}
+
+function test_getFiles(aDirectory, aRecursive, aNext) {
+  aDirectory
+    .getFiles(aRecursive)
+    .then(
+      function (data) {
+        for (var i = 0; i < data.length; ++i) {
+          ok(data[i] instanceof File, "File: " + data[i].name);
+          is(aDirectory.path[0], "/", "Directory path must start with '/'");
+          ok(
+            data[i].webkitRelativePath.indexOf(aDirectory.path.substring(1)) ==
+              0 &&
+              data[i].webkitRelativePath.indexOf("/" + data[i].name) +
+                ("/" + data[i].name).length ==
+                data[i].webkitRelativePath.length,
+            "File.webkitRelativePath should be called dir.path + '/' + file.name: " +
+              data[i].webkitRelativePath
+          );
+        }
+      },
+      function () {
+        ok(false, "Something when wrong");
+      }
+    )
+    .then(aNext);
+}
+
+function test_getFiles_recursiveComparison(aDirectory, aNext) {
+  aDirectory
+    .getFiles(true)
+    .then(function (data) {
+      is(data.length, 2, "Only 2 files for this test.");
+      ok(
+        data[0].name == "foo.txt" || data[0].name == "bar.txt",
+        "First filename matches"
+      );
+      ok(
+        data[1].name == "foo.txt" || data[1].name == "bar.txt",
+        "Second filename matches"
+      );
+    })
+    .then(function () {
+      return aDirectory.getFiles(false);
+    })
+    .then(function (data) {
+      is(data.length, 1, "Only 1 file for this test.");
+      ok(
+        data[0].name == "foo.txt" || data[0].name == "bar.txt",
+        "First filename matches"
+      );
+    })
+    .catch(function () {
+      ok(false, "Something when wrong");
+    })
+    .then(aNext);
+}
diff --git a/dom/filesystem/tests/mochitest.toml b/dom/filesystem/tests/mochitest.toml
new file mode 100644
index 0000000000..869fe2d37f
--- /dev/null
+++ b/dom/filesystem/tests/mochitest.toml
@@ -0,0 +1,16 @@
+[DEFAULT]
+support-files = [
+  "filesystem_commons.js",
+  "script_fileList.js",
+  "worker_basic.js",
+]
+
+["test_basic.html"]
+
+["test_bug1319088.html"]
+
+["test_webkitdirectory.html"]
+skip-if = ["os == 'android'"] # Bug 1674428
+support-files = ["script_promptHandler.js"]
+
+["test_worker_basic.html"]
diff --git a/dom/filesystem/tests/moz.build b/dom/filesystem/tests/moz.build
new file mode 100644
index 0000000000..2f41008128
--- /dev/null
+++ b/dom/filesystem/tests/moz.build
@@ -0,0 +1,7 @@
+# -*- 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/.
+
+MOCHITEST_MANIFESTS += ["mochitest.toml"]
diff --git a/dom/filesystem/tests/script_fileList.js b/dom/filesystem/tests/script_fileList.js
new file mode 100644
index 0000000000..47438aa7b3
--- /dev/null
+++ b/dom/filesystem/tests/script_fileList.js
@@ -0,0 +1,176 @@
+/* eslint-env mozilla/chrome-script */
+// eslint-disable-next-line mozilla/reject-importGlobalProperties
+Cu.importGlobalProperties(["File"]);
+function createProfDFile() {
+  return Services.dirsvc
+    .QueryInterface(Ci.nsIProperties)
+    .get("ProfD", Ci.nsIFile);
+}
+
+const { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+
+// Creates a parametric arity directory hierarchy as a function of depth.
+// Each directory contains one leaf file, and subdirectories of depth [1, depth).
+// e.g. for depth 3:
+//
+// subdir3
+// - file.txt
+// - subdir2
+//   - file.txt
+//   - subdir1
+//     - file.txt
+// - subdir1
+//   - file.txt
+//
+// Returns the parent directory of the subtree.
+function createTreeFile(depth, parent) {
+  if (!parent) {
+    parent = Services.dirsvc
+      .QueryInterface(Ci.nsIProperties)
+      .get("TmpD", Ci.nsIFile);
+    parent.append("dir-tree-test");
+    parent.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0o700);
+  }
+
+  var nextFile = parent.clone();
+  if (depth == 0) {
+    nextFile.append("file.txt");
+    nextFile.create(Ci.nsIFile.NORMAL_FILE_TYPE, 0o600);
+
+    // It's not possible to create symlinks on windows by default or on our
+    // Android platforms, so we can't create the symlink file there.  Our
+    // callers that care are aware of this and also check AppConstants.
+    if (
+      AppConstants.platform !== "win" &&
+      AppConstants.platform !== "android"
+    ) {
+      var linkFile = parent.clone();
+      linkFile.append("symlink.txt");
+      createSymLink(nextFile.path, linkFile.path);
+    }
+  } else {
+    nextFile.append("subdir" + depth);
+    nextFile.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0o700);
+    // Decrement the maximal depth by one for each level of nesting.
+    for (var i = 0; i < depth; i++) {
+      createTreeFile(i, nextFile);
+    }
+  }
+
+  return parent;
+}
+
+function createRootFile() {
+  var testFile = createProfDFile();
+
+  // Let's go back to the root of the FileSystem
+  while (true) {
+    var parent = testFile.parent;
+    if (!parent) {
+      break;
+    }
+
+    testFile = parent;
+  }
+
+  return testFile;
+}
+
+var process;
+function createSymLink(target, linkName) {
+  if (!process) {
+    var ln = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsIFile);
+    ln.initWithPath("/bin/ln");
+
+    process = Cc["@mozilla.org/process/util;1"].createInstance(Ci.nsIProcess);
+    process.init(ln);
+  }
+
+  const args = ["-s", target, linkName];
+  process.run(true, args, args.length);
+  Assert.equal(process.exitValue, 0);
+}
+
+function createTestFile() {
+  var tmpFile = Services.dirsvc
+    .QueryInterface(Ci.nsIProperties)
+    .get("TmpD", Ci.nsIFile);
+  tmpFile.append("dir-test");
+  tmpFile.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0o700);
+
+  var file1 = tmpFile.clone();
+  file1.append("foo.txt");
+  file1.create(Ci.nsIFile.NORMAL_FILE_TYPE, 0o600);
+
+  var dir = tmpFile.clone();
+  dir.append("subdir");
+  dir.create(Ci.nsIFile.DIRECTORY_TYPE, 0o700);
+
+  var file2 = dir.clone();
+  file2.append("bar.txt");
+  file2.create(Ci.nsIFile.NORMAL_FILE_TYPE, 0o600);
+
+  // It's not possible to create symlinks on windows by default or on our
+  // Android platforms, so we can't create the symlink file there.  Our
+  // callers that care are aware of this and also check AppConstants.
+  if (AppConstants.platform !== "win" && AppConstants.platform !== "android") {
+    var linkFile = dir.clone();
+    linkFile.append("symlink.txt");
+    createSymLink(file1.path, linkFile.path);
+  }
+
+  return tmpFile;
+}
+
+addMessageListener("dir.open", function (e) {
+  var testFile;
+
+  switch (e.path) {
+    case "ProfD":
+      // Note that files in the profile directory are not guaranteed to persist-
+      // see bug 1284742.
+      testFile = createProfDFile();
+      break;
+
+    case "root":
+      testFile = createRootFile();
+      break;
+
+    case "test":
+      testFile = createTestFile();
+      break;
+
+    case "tree":
+      testFile = createTreeFile(3);
+      break;
+  }
+
+  sendAsyncMessage("dir.opened", {
+    dir: testFile.path,
+    name: testFile.leafName,
+  });
+});
+
+addMessageListener("file.open", function (e) {
+  var testFile = Services.dirsvc
+    .QueryInterface(Ci.nsIProperties)
+    .get("ProfD", Ci.nsIFile);
+  testFile.append("prefs.js");
+
+  File.createFromNsIFile(testFile).then(function (file) {
+    sendAsyncMessage("file.opened", { file });
+  });
+});
+
+addMessageListener("symlink.open", function (e) {
+  let testDir = createTestFile();
+  let testFile = testDir.clone();
+  testFile.append("subdir");
+  testFile.append("symlink.txt");
+
+  File.createFromNsIFile(testFile).then(function (file) {
+    sendAsyncMessage("symlink.opened", { dir: testDir.path, file });
+  });
+});
diff --git a/dom/filesystem/tests/script_promptHandler.js b/dom/filesystem/tests/script_promptHandler.js
new file mode 100644
index 0000000000..ed3bda7404
--- /dev/null
+++ b/dom/filesystem/tests/script_promptHandler.js
@@ -0,0 +1,18 @@
+/* eslint-env mozilla/chrome-script */
+
+let dialogObserverTopic = "common-dialog-loaded";
+
+function dialogObserver(subj, topic, data) {
+  subj.document.querySelector("dialog").acceptDialog();
+  sendAsyncMessage("promptAccepted");
+}
+
+addMessageListener("init", message => {
+  Services.obs.addObserver(dialogObserver, dialogObserverTopic);
+  sendAsyncMessage("initDone");
+});
+
+addMessageListener("cleanup", message => {
+  Services.obs.removeObserver(dialogObserver, dialogObserverTopic);
+  sendAsyncMessage("cleanupDone");
+});
diff --git a/dom/filesystem/tests/test_basic.html b/dom/filesystem/tests/test_basic.html
new file mode 100644
index 0000000000..b4daea79c9
--- /dev/null
+++ b/dom/filesystem/tests/test_basic.html
@@ -0,0 +1,118 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for Directory API</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="filesystem_commons.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+
+<body>
+<script type="application/javascript">
+
+var directory;
+var fileList;
+
+function create_fileList(aPath) {
+  fileList = document.createElement("input");
+  fileList.setAttribute("type", "file");
+  document.body.appendChild(fileList);
+
+  var url = SimpleTest.getTestFileURL("script_fileList.js");
+  var script = SpecialPowers.loadChromeScript(url);
+
+  function onOpened(message) {
+    SpecialPowers.wrap(fileList).mozSetDirectory(message.dir);
+    fileList.setAttribute("data-name", message.name);
+
+    SpecialPowers.wrap(fileList).getFilesAndDirectories().then(function(array) {
+      array =  SpecialPowers.unwrap(array);
+      is(array.length, 1, "We want just 1 directory.");
+      ok(array[0] instanceof Directory, "We want just 1 directory.");
+
+      directory = array[0];
+      script.destroy();
+      next();
+    });
+  }
+
+  script.addMessageListener("dir.opened", onOpened);
+  script.sendAsyncMessage("dir.open", { path: aPath });
+}
+
+function test_simpleFilePicker(aPath) {
+  var url = SimpleTest.getTestFileURL("script_fileList.js");
+  var script = SpecialPowers.loadChromeScript(url);
+
+  function onOpened(message) {
+    SpecialPowers.wrap(fileList).mozSetFileArray([message.file]);
+
+    is(fileList.files.length, 1, "we want 1 element");
+    ok(fileList.files[0] instanceof File, "we want 1 file");
+    ok("webkitRelativePath" in fileList.files[0], "we have webkitRelativePath attribute");
+    is(fileList.files[0].webkitRelativePath, "", "No webkit relative path for normal filePicker");
+
+    script.destroy();
+    next();
+  }
+
+  script.addMessageListener("file.opened", onOpened);
+  script.sendAsyncMessage("file.open");
+}
+
+function test_duplicateGetFilesAndDirectories() {
+  var url = SimpleTest.getTestFileURL("script_fileList.js");
+  var script = SpecialPowers.loadChromeScript(url);
+
+  function onOpened(message) {
+    SpecialPowers.wrap(fileList).mozSetDirectory(message.dir);
+
+    var p1 = SpecialPowers.wrap(fileList).getFilesAndDirectories();
+    var p2 = SpecialPowers.wrap(fileList).getFilesAndDirectories();
+
+    isnot(p1, p2, "We create 2 different promises");
+
+    script.destroy();
+    next();
+  }
+
+  script.addMessageListener("dir.opened", onOpened);
+  script.sendAsyncMessage("dir.open", { path: "test" });
+}
+
+var tests = [
+  function() { setup_tests(next); },
+
+  function() { create_fileList("tree"); },
+  function() { test_basic(directory, next); },
+  function() { test_getFilesAndDirectories(directory, true, next); },
+  function() { test_getFiles(directory, false, next); },
+  function() { test_getFiles(directory, true, next); },
+
+  function() { create_fileList("test"); },
+  function() { test_getFiles_recursiveComparison(directory, next); },
+
+  function() { create_fileList("root"); },
+  function() { test_basic(directory, next); },
+  function() { test_getFilesAndDirectories(directory, false, next); },
+  function() { test_getFiles(directory, false, next); },
+
+  test_duplicateGetFilesAndDirectories,
+  test_simpleFilePicker,
+];
+
+function next() {
+  if (!tests.length) {
+    SimpleTest.finish();
+    return;
+  }
+
+  var test = tests.shift();
+  test();
+}
+
+SimpleTest.waitForExplicitFinish();
+next();
+</script>
+</body>
+</html>
diff --git a/dom/filesystem/tests/test_bug1319088.html b/dom/filesystem/tests/test_bug1319088.html
new file mode 100644
index 0000000000..98e0ad46f0
--- /dev/null
+++ b/dom/filesystem/tests/test_bug1319088.html
@@ -0,0 +1,65 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for bug 1319088</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+
+<body>
+<input id="input" type="file"></input>
+
+<script type="application/javascript">
+
+function testSetup() {
+  SpecialPowers.pushPrefEnv({"set": [["dom.webkitBlink.dirPicker.enabled", true]]}, next);
+}
+
+function populateInputFile() {
+  var url = SimpleTest.getTestFileURL("script_fileList.js");
+  var script = SpecialPowers.loadChromeScript(url);
+
+  function onOpened(message) {
+    var input = document.getElementById("input");
+    SpecialPowers.wrap(input).mozSetFileArray([message.file]);
+
+    script.destroy();
+    next();
+  }
+
+  script.addMessageListener("file.opened", onOpened);
+  script.sendAsyncMessage("file.open");
+}
+
+function checkBug() {
+  var input = document.getElementById("input");
+  is(input.files[0].webkitRelativePath, "", "No relative path!");
+
+  let form = document.createElement("form");
+  form.appendChild(input);
+
+  is(input.files[0].webkitRelativePath, "", "No relative path!");
+  SimpleTest.finish();
+}
+
+var tests = [
+  testSetup,
+  populateInputFile,
+  checkBug,
+];
+
+function next() {
+  if (!tests.length) {
+    SimpleTest.finish();
+    return;
+  }
+
+  var test = tests.shift();
+  test();
+}
+
+SimpleTest.waitForExplicitFinish();
+next();
+</script>
+</body>
+</html>
diff --git a/dom/filesystem/tests/test_webkitdirectory.html b/dom/filesystem/tests/test_webkitdirectory.html
new file mode 100644
index 0000000000..50080ad7ba
--- /dev/null
+++ b/dom/filesystem/tests/test_webkitdirectory.html
@@ -0,0 +1,309 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for webkitdirectory and webkitRelativePath</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+
+<body>
+<input id="inputFileWebkitDirectory" type="file" webkitdirectory></input>
+<input id="inputFileWebkitFile" type="file"></input>
+<input id="inputFileDirectoryChange" type="file" webkitdirectory></input>
+
+<script type="application/javascript">
+
+const { AppConstants } = SpecialPowers.ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+
+let promptHandler;
+
+function waitForEvent(element, eventName) {
+  return new Promise(function(resolve) {
+    element.addEventListener(eventName, e => resolve(e.detail), { once: true });
+  });
+}
+
+function waitForPromptHandled() {
+  return new Promise(resolve => promptHandler.addMessageListener("promptAccepted", resolve));
+}
+
+// Populate the given input type=file `aInputFile`'s `files` attribute by:
+// - loading `script_fileList.js` in the parent process
+// - telling it to generate the "test" template directory pattern which will
+//   create "foo.txt", "subdir/bar.txt", and if symlinks are available on the
+//   platform, "symlink.txt" which will be a symlink to "foo.txt".  (Note that
+//   we explicitly expect the symlink to be filtered out if generated, and
+//   during the enhancement of the test we verified the file was created on
+//   linux by running the test before fixing the GetFilesHelper logic to filter
+//   the symlink out and verifying the subsequent `test_fileList` check failed.)
+// - Triggering the mock file picker with the base directory of the "test"
+//   template directory.
+//
+// It's expected that `test_fileList` will be used after this step completes in
+// order to validate the results.
+function populateInputFile(aInputFile) {
+  var url = SimpleTest.getTestFileURL("script_fileList.js");
+  var script = SpecialPowers.loadChromeScript(url);
+
+  var MockFilePicker = SpecialPowers.MockFilePicker;
+  MockFilePicker.init(window, "A Mock File Picker", SpecialPowers.Ci.nsIFilePicker.modeGetFolder);
+
+  async function onOpened(message) {
+    MockFilePicker.useDirectory(message.dir);
+
+    let input = document.getElementById(aInputFile);
+    input.setAttribute("data-name", message.name);
+
+    let promptHandled = waitForPromptHandled();
+    let changeEvent = waitForEvent(input, "change");
+
+    input.click();
+
+    await promptHandled;
+    await changeEvent;
+
+    MockFilePicker.cleanup();
+    script.destroy();
+    next();
+  }
+
+  script.addMessageListener("dir.opened", onOpened);
+  script.sendAsyncMessage("dir.open", { path: "test" });
+}
+
+function checkFile(file, fileList, dirName) {
+  for (var i = 0; i < fileList.length; ++i) {
+    ok(fileList[i] instanceof File, "We want just files.");
+    if (fileList[i].name == file.name) {
+      is(fileList[i].webkitRelativePath, dirName + file.path, "Path matches");
+      return;
+    }
+  }
+
+  ok(false, "File not found.");
+}
+
+// Validate the contents of the given input type=file `aInputFile`'s' `files`
+// property against the expected list of files `aWhat`.
+function test_fileList(aInputFile, aWhat) {
+  var input = document.getElementById(aInputFile);
+  var fileList = input.files;
+
+  if (aWhat == null) {
+    is(fileList, null, "We want a null fileList for " + aInputFile);
+    next();
+    return;
+  }
+
+  is(fileList.length, aWhat.length, "We want just " + aWhat.length + " elements for " + aInputFile);
+  for (var i = 0; i < aWhat.length; ++i) {
+    checkFile(aWhat[i], fileList, input.dataset.name);
+  }
+
+  next();
+}
+
+// Verify that we can explicitly select a symlink and it will not be filtered
+// out.  This is really a verification that GetFileHelper's file-handling logic
+// https://searchfox.org/mozilla-central/rev/065102493dfc49234120c37fc6a334a5b1d86d9e/dom/filesystem/GetFilesHelper.cpp#81-86
+// does not proactively take an action to filter out a selected symlink.
+//
+// This is a glass box test that is not entirely realistic for our actual system
+// file pickers but does reflect what will happen in the drag-and-drop case
+// for `HTMLInputElement::MozSetDndFilesAndDirectories` and this helps ensure
+// that future implementation changes will behave as expected.  Specifically,
+// the presence of webkitdirectory will result in the file picker using
+// `modeGetFolder` which will only allow selection of a directory and forbid
+// file selection.
+//
+// This test explicitly does not validate HTMLInputElement's non-webkitdirectory
+// file selection mechanism because it does not involve GetFileHelper.
+async function test_individualSymlink(aInputFile) {
+  const input = document.getElementById(aInputFile);
+
+  // -- Create the symlink and get a `File` instance pointing at it.
+  const url = SimpleTest.getTestFileURL("script_fileList.js");
+  const script = SpecialPowers.loadChromeScript(url);
+
+  let opened = new Promise(resolve => script.addMessageListener("symlink.opened", resolve));
+  script.sendAsyncMessage("symlink.open", {});
+  let { dir, file: symlinkFile } = await opened;
+  info(`symlink.open provided dir: ${dir}`)
+
+  // -- Have the picker pick it
+  var MockFilePicker = SpecialPowers.MockFilePicker;
+  MockFilePicker.init(window, "A Mock File Picker", SpecialPowers.Ci.nsIFilePicker.modeOpen);
+
+  MockFilePicker.displayDirectory = dir;
+  let pickerShown = new Promise(resolve => {
+    MockFilePicker.showCallback = function() {
+      // This is where we are diverging from a realistic scenario in order to get
+      // the expected coverage.
+      MockFilePicker.setFiles([symlinkFile]);
+      resolve();
+    }
+  });
+  MockFilePicker.returnValue = MockFilePicker.returnOK;
+
+  let changeEvent = waitForEvent(input, "change");
+
+  input.click();
+
+  await pickerShown;
+  await changeEvent;
+
+  MockFilePicker.cleanup();
+  script.destroy();
+
+  // -- Verify that we see the symlink.
+  let fileList = input.files;
+  is(fileList.length, 1, "There should be 1 file.");
+  is(fileList[0].name, "symlink.txt", "The file should be the symlink.");
+  next();
+}
+
+function test_webkitdirectory_attribute() {
+  var a = document.createElement("input");
+  a.setAttribute("type", "file");
+
+  ok("webkitdirectory" in a, "HTMLInputElement.webkitdirectory exists");
+
+  ok(!a.hasAttribute("webkitdirectory"), "No webkitdirectory DOM attribute by default");
+  ok(!a.webkitdirectory, "No webkitdirectory attribute by default");
+
+  a.webkitdirectory = true;
+
+  ok(a.hasAttribute("webkitdirectory"), "Webkitdirectory DOM attribute is set");
+  ok(a.webkitdirectory, "Webkitdirectory attribute is set");
+
+  next();
+}
+
+function test_changeDataWhileWorking() {
+  var url = SimpleTest.getTestFileURL("script_fileList.js");
+  var script = SpecialPowers.loadChromeScript(url);
+
+  var MockFilePicker = SpecialPowers.MockFilePicker;
+  MockFilePicker.init(window, "A Mock File Picker", SpecialPowers.Ci.nsIFilePicker.modeGetFolder);
+  let promptHandled;
+
+  // Let's start retrieving the root nsIFile object
+  new Promise(function(resolve) {
+    function onOpened(message) {
+      script.removeMessageListener("dir.opened", onOpened);
+      resolve(message.dir);
+    }
+
+    script.addMessageListener("dir.opened", onOpened);
+    script.sendAsyncMessage("dir.open", { path: "root" });
+  })
+
+  // input.click() pointing to the root dir
+  .then(async function(aDir) {
+    MockFilePicker.cleanup();
+    MockFilePicker.init(window, "A Mock File Picker", SpecialPowers.Ci.nsIFilePicker.modeGetFolder);
+    MockFilePicker.useDirectory(aDir);
+    var input = document.getElementById("inputFileDirectoryChange");
+
+    promptHandled = waitForPromptHandled();
+    input.click();
+  })
+
+  // Before onchange, let's take the 'test' directory
+  .then(function() {
+    return new Promise(function(resolve) {
+      function onOpened(message) {
+        script.removeMessageListener("dir.opened", onOpened);
+        script.destroy();
+        resolve(message.dir);
+      }
+
+      script.addMessageListener("dir.opened", onOpened);
+      script.sendAsyncMessage("dir.open", { path: "test" });
+    });
+  })
+
+  // Now let's click again and wait for onchange.
+  .then(async function(aDir) {
+      MockFilePicker.cleanup();
+      MockFilePicker.init(window, "A Mock File Picker", SpecialPowers.Ci.nsIFilePicker.modeGetFolder);
+      MockFilePicker.useDirectory(aDir);
+
+      let input = document.getElementById("inputFileDirectoryChange");
+      let changeEvent = waitForEvent(input, "change");
+
+      input.click();
+
+      await promptHandled;
+      await changeEvent;
+
+      MockFilePicker.cleanup();
+  })
+  .then(function() {
+    test_fileList("inputFileWebkitDirectory", testDirData);
+  });
+}
+
+async function test_setup() {
+  let promptHandlerUrl = SimpleTest.getTestFileURL("script_promptHandler.js")
+  promptHandler = SpecialPowers.loadChromeScript(promptHandlerUrl);
+
+  let promptHandlerReady = new Promise(resolve => promptHandler.addMessageListener("initDone", resolve));
+  promptHandler.sendAsyncMessage("init");
+  await promptHandlerReady;
+
+  SpecialPowers.pushPrefEnv({"set": [["dom.filesystem.pathcheck.disabled", true],
+                                     ["dom.webkitBlink.dirPicker.enabled", true]]}, next);
+}
+
+async function test_cleanup() {
+  let promptHandlerDone = new Promise(resolve => promptHandler.addMessageListener("cleanupDone", resolve));
+  promptHandler.sendAsyncMessage("cleanup");
+  await promptHandlerDone;
+  promptHandler.destroy();
+}
+
+var testDirData = [ { name: "foo.txt", path: "/foo.txt" },
+                    { name: "bar.txt", path: "/subdir/bar.txt" }];
+
+var tests = [
+  test_setup,
+
+  function() { populateInputFile("inputFileWebkitDirectory"); },
+
+  function() { test_fileList("inputFileWebkitDirectory", testDirData); },
+
+  function() {
+    // Symlinks are not available on Windows and so will not be created.
+    if (AppConstants.platform === "win" || AppConstants.platform === "android") {
+      info("Skipping individual symlink check on Windows and Android.");
+      next();
+      return;
+    }
+
+    test_individualSymlink("inputFileWebkitFile").catch(err => ok(false, `Problem in symlink case: ${err}`));
+  },
+
+  test_webkitdirectory_attribute,
+
+  test_changeDataWhileWorking,
+];
+
+async function next() {
+  if (!tests.length) {
+    await test_cleanup();
+    SimpleTest.finish();
+    return;
+  }
+
+  var test = tests.shift();
+  await test();
+}
+
+SimpleTest.waitForExplicitFinish();
+next();
+</script>
+</body>
+</html>
diff --git a/dom/filesystem/tests/test_worker_basic.html b/dom/filesystem/tests/test_worker_basic.html
new file mode 100644
index 0000000000..920f32719b
--- /dev/null
+++ b/dom/filesystem/tests/test_worker_basic.html
@@ -0,0 +1,73 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for Directory API in workers</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="filesystem_commons.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+
+<body>
+<script type="application/javascript">
+
+var fileList;
+
+function create_fileList() {
+  fileList = document.createElement("input");
+  fileList.setAttribute("type", "file");
+  document.body.appendChild(fileList);
+
+  var url = SimpleTest.getTestFileURL("script_fileList.js");
+  var script = SpecialPowers.loadChromeScript(url);
+
+  function onOpened(message) {
+    SpecialPowers.wrap(fileList).mozSetDirectory(message.dir);
+    script.destroy();
+    next();
+  }
+
+  script.addMessageListener("dir.opened", onOpened);
+  script.sendAsyncMessage("dir.open", { path: "test" });
+}
+
+function test_worker() {
+  SpecialPowers.wrap(fileList).getFilesAndDirectories().then(function(array) {
+    array = SpecialPowers.unwrap(array);
+    var worker = new Worker("worker_basic.js");
+    worker.onmessage = function(e) {
+      if (e.data.type == "finish") {
+        next();
+        return;
+      }
+
+      if (e.data.type == "test") {
+        ok(e.data.test, e.data.message);
+      }
+    };
+
+    worker.postMessage(array[0]);
+  });
+}
+
+var tests = [
+  function() { setup_tests(next); },
+
+  create_fileList,
+  test_worker,
+];
+
+function next() {
+  if (!tests.length) {
+    SimpleTest.finish();
+    return;
+  }
+
+  var test = tests.shift();
+  test();
+}
+
+SimpleTest.waitForExplicitFinish();
+next();
+</script>
+</body>
+</html>
diff --git a/dom/filesystem/tests/worker_basic.js b/dom/filesystem/tests/worker_basic.js
new file mode 100644
index 0000000000..2771c778fd
--- /dev/null
+++ b/dom/filesystem/tests/worker_basic.js
@@ -0,0 +1,50 @@
+/* eslint-env worker */
+importScripts("filesystem_commons.js");
+
+function finish() {
+  postMessage({ type: "finish" });
+}
+
+function ok(a, msg) {
+  postMessage({ type: "test", test: !!a, message: msg });
+}
+
+function is(a, b, msg) {
+  ok(a === b, msg);
+}
+
+function isnot(a, b, msg) {
+  ok(a != b, msg);
+}
+
+var tests = [
+  function () {
+    test_basic(directory, next);
+  },
+  function () {
+    test_getFilesAndDirectories(directory, true, next);
+  },
+  function () {
+    test_getFiles(directory, false, next);
+  },
+  function () {
+    test_getFiles(directory, true, next);
+  },
+];
+
+function next() {
+  if (!tests.length) {
+    finish();
+    return;
+  }
+
+  var test = tests.shift();
+  test();
+}
+
+var directory;
+
+onmessage = function (e) {
+  directory = e.data;
+  next();
+};