Adding upstream version 115.7.0esr.upstream/115.7.0esr

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

18 files changed, 2620 insertions, 0 deletions

diff --git a/ipc/mscom/Aggregation.h b/ipc/mscom/Aggregation.h
new file mode 100644
index 0000000000..ca171e39cc
--- /dev/null
+++ b/ipc/mscom/Aggregation.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_mscom_Aggregation_h
+#define mozilla_mscom_Aggregation_h
+
+#include "mozilla/Attributes.h"
+
+#include <stddef.h>
+#include <unknwn.h>
+
+namespace mozilla {
+namespace mscom {
+
+/**
+ * This is used for stabilizing a COM object's reference count during
+ * construction when that object aggregates other objects. Since the aggregated
+ * object(s) may AddRef() or Release(), we need to artifically boost the
+ * refcount to prevent premature destruction. Note that we increment/decrement
+ * instead of AddRef()/Release() in this class because we want to adjust the
+ * refcount without causing any other side effects (like object destruction).
+ */
+template <typename RefCntT>
+class MOZ_RAII StabilizedRefCount {
+ public:
+  explicit StabilizedRefCount(RefCntT& aRefCnt) : mRefCnt(aRefCnt) {
+    ++aRefCnt;
+  }
+
+  ~StabilizedRefCount() { --mRefCnt; }
+
+  StabilizedRefCount(const StabilizedRefCount&) = delete;
+  StabilizedRefCount(StabilizedRefCount&&) = delete;
+  StabilizedRefCount& operator=(const StabilizedRefCount&) = delete;
+  StabilizedRefCount& operator=(StabilizedRefCount&&) = delete;
+
+ private:
+  RefCntT& mRefCnt;
+};
+
+namespace detail {
+
+template <typename T>
+class InternalUnknown : public IUnknown {
+ public:
+  STDMETHODIMP QueryInterface(REFIID aIid, void** aOutInterface) override {
+    return This()->InternalQueryInterface(aIid, aOutInterface);
+  }
+
+  STDMETHODIMP_(ULONG) AddRef() override { return This()->InternalAddRef(); }
+
+  STDMETHODIMP_(ULONG) Release() override { return This()->InternalRelease(); }
+
+ private:
+  T* This() {
+    return reinterpret_cast<T*>(reinterpret_cast<char*>(this) -
+                                offsetof(T, mInternalUnknown));
+  }
+};
+
+}  // namespace detail
+}  // namespace mscom
+}  // namespace mozilla
+
+#define DECLARE_AGGREGATABLE(Type)                                      \
+ public:                                                                \
+  STDMETHODIMP QueryInterface(REFIID riid, void** ppv) override {       \
+    return mOuter->QueryInterface(riid, ppv);                           \
+  }                                                                     \
+  STDMETHODIMP_(ULONG) AddRef() override { return mOuter->AddRef(); }   \
+  STDMETHODIMP_(ULONG) Release() override { return mOuter->Release(); } \
+                                                                        \
+ protected:                                                             \
+  STDMETHODIMP InternalQueryInterface(REFIID riid, void** ppv);         \
+  STDMETHODIMP_(ULONG) InternalAddRef();                                \
+  STDMETHODIMP_(ULONG) InternalRelease();                               \
+  friend class mozilla::mscom::detail::InternalUnknown<Type>;           \
+  mozilla::mscom::detail::InternalUnknown<Type> mInternalUnknown
+
+#endif  // mozilla_mscom_Aggregation_h
diff --git a/ipc/mscom/AgileReference.cpp b/ipc/mscom/AgileReference.cpp
new file mode 100644
index 0000000000..7a1b94822d
--- /dev/null
+++ b/ipc/mscom/AgileReference.cpp
@@ -0,0 +1,223 @@
+/* -*- 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/mscom/AgileReference.h"
+
+#include <utility>
+
+#include "mozilla/Assertions.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/DynamicallyLinkedFunctionPtr.h"
+#include "mozilla/mscom/Utils.h"
+
+#if defined(MOZILLA_INTERNAL_API)
+#  include "nsDebug.h"
+#  include "nsPrintfCString.h"
+#endif  // defined(MOZILLA_INTERNAL_API)
+
+#if NTDDI_VERSION < NTDDI_WINBLUE
+
+// Declarations from Windows SDK specific to Windows 8.1
+
+enum AgileReferenceOptions {
+  AGILEREFERENCE_DEFAULT = 0,
+  AGILEREFERENCE_DELAYEDMARSHAL = 1,
+};
+
+HRESULT WINAPI RoGetAgileReference(AgileReferenceOptions options, REFIID riid,
+                                   IUnknown* pUnk,
+                                   IAgileReference** ppAgileReference);
+
+#endif  // NTDDI_VERSION < NTDDI_WINBLUE
+
+namespace mozilla {
+namespace mscom {
+namespace detail {
+
+GlobalInterfaceTableCookie::GlobalInterfaceTableCookie(IUnknown* aObject,
+                                                       REFIID aIid,
+                                                       HRESULT& aOutHResult)
+    : mCookie(0) {
+  IGlobalInterfaceTable* git = ObtainGit();
+  MOZ_ASSERT(git);
+  if (!git) {
+    aOutHResult = E_POINTER;
+    return;
+  }
+
+  aOutHResult = git->RegisterInterfaceInGlobal(aObject, aIid, &mCookie);
+  MOZ_ASSERT(SUCCEEDED(aOutHResult));
+}
+
+GlobalInterfaceTableCookie::~GlobalInterfaceTableCookie() {
+  IGlobalInterfaceTable* git = ObtainGit();
+  MOZ_ASSERT(git);
+  if (!git) {
+    return;
+  }
+
+  DebugOnly<HRESULT> hr = git->RevokeInterfaceFromGlobal(mCookie);
+#if defined(MOZILLA_INTERNAL_API)
+  NS_WARNING_ASSERTION(
+      SUCCEEDED(hr),
+      nsPrintfCString("IGlobalInterfaceTable::RevokeInterfaceFromGlobal failed "
+                      "with HRESULT 0x%08lX",
+                      ((HRESULT)hr))
+          .get());
+#else
+  MOZ_ASSERT(SUCCEEDED(hr));
+#endif  // defined(MOZILLA_INTERNAL_API)
+  mCookie = 0;
+}
+
+HRESULT GlobalInterfaceTableCookie::GetInterface(REFIID aIid,
+                                                 void** aOutInterface) const {
+  IGlobalInterfaceTable* git = ObtainGit();
+  MOZ_ASSERT(git);
+  if (!git) {
+    return E_UNEXPECTED;
+  }
+
+  MOZ_ASSERT(IsValid());
+  return git->GetInterfaceFromGlobal(mCookie, aIid, aOutInterface);
+}
+
+/* static */
+IGlobalInterfaceTable* GlobalInterfaceTableCookie::ObtainGit() {
+  // Internally to COM, the Global Interface Table is a singleton, therefore we
+  // don't worry about holding onto this reference indefinitely.
+  static IGlobalInterfaceTable* sGit = []() -> IGlobalInterfaceTable* {
+    IGlobalInterfaceTable* result = nullptr;
+    DebugOnly<HRESULT> hr = ::CoCreateInstance(
+        CLSID_StdGlobalInterfaceTable, nullptr, CLSCTX_INPROC_SERVER,
+        IID_IGlobalInterfaceTable, reinterpret_cast<void**>(&result));
+    MOZ_ASSERT(SUCCEEDED(hr));
+    return result;
+  }();
+
+  return sGit;
+}
+
+}  // namespace detail
+
+AgileReference::AgileReference() : mIid(), mHResult(E_NOINTERFACE) {}
+
+AgileReference::AgileReference(REFIID aIid, IUnknown* aObject)
+    : mIid(aIid), mHResult(E_UNEXPECTED) {
+  AssignInternal(aObject);
+}
+
+AgileReference::AgileReference(AgileReference&& aOther)
+    : mIid(aOther.mIid),
+      mAgileRef(std::move(aOther.mAgileRef)),
+      mGitCookie(std::move(aOther.mGitCookie)),
+      mHResult(aOther.mHResult) {
+  aOther.mHResult = CO_E_RELEASED;
+}
+
+void AgileReference::Assign(REFIID aIid, IUnknown* aObject) {
+  Clear();
+  mIid = aIid;
+  AssignInternal(aObject);
+}
+
+void AgileReference::AssignInternal(IUnknown* aObject) {
+  // We expect mIid to already be set
+  DebugOnly<IID> zeroIid = {};
+  MOZ_ASSERT(mIid != zeroIid);
+
+  /*
+   * There are two possible techniques for creating agile references. Starting
+   * with Windows 8.1, we may use the RoGetAgileReference API, which is faster.
+   * If that API is not available, we fall back to using the Global Interface
+   * Table.
+   */
+  static const StaticDynamicallyLinkedFunctionPtr<
+      decltype(&::RoGetAgileReference)>
+      pRoGetAgileReference(L"ole32.dll", "RoGetAgileReference");
+
+  MOZ_ASSERT(aObject);
+
+  if (pRoGetAgileReference &&
+      SUCCEEDED(mHResult =
+                    pRoGetAgileReference(AGILEREFERENCE_DEFAULT, mIid, aObject,
+                                         getter_AddRefs(mAgileRef)))) {
+    return;
+  }
+
+  mGitCookie = new detail::GlobalInterfaceTableCookie(aObject, mIid, mHResult);
+  MOZ_ASSERT(mGitCookie->IsValid());
+}
+
+AgileReference::~AgileReference() { Clear(); }
+
+void AgileReference::Clear() {
+  mIid = {};
+  mAgileRef = nullptr;
+  mGitCookie = nullptr;
+  mHResult = E_NOINTERFACE;
+}
+
+AgileReference& AgileReference::operator=(const AgileReference& aOther) {
+  Clear();
+  mIid = aOther.mIid;
+  mAgileRef = aOther.mAgileRef;
+  mGitCookie = aOther.mGitCookie;
+  mHResult = aOther.mHResult;
+  return *this;
+}
+
+AgileReference& AgileReference::operator=(AgileReference&& aOther) {
+  Clear();
+  mIid = aOther.mIid;
+  mAgileRef = std::move(aOther.mAgileRef);
+  mGitCookie = std::move(aOther.mGitCookie);
+  mHResult = aOther.mHResult;
+  aOther.mHResult = CO_E_RELEASED;
+  return *this;
+}
+
+HRESULT
+AgileReference::Resolve(REFIID aIid, void** aOutInterface) const {
+  MOZ_ASSERT(aOutInterface);
+  // This check is exclusive-OR; we should have one or the other, but not both
+  MOZ_ASSERT((mAgileRef || mGitCookie) && !(mAgileRef && mGitCookie));
+  MOZ_ASSERT(IsCOMInitializedOnCurrentThread());
+
+  if (!aOutInterface) {
+    return E_INVALIDARG;
+  }
+
+  *aOutInterface = nullptr;
+
+  if (mAgileRef) {
+    // IAgileReference lets you directly resolve the interface you want...
+    return mAgileRef->Resolve(aIid, aOutInterface);
+  }
+
+  if (!mGitCookie) {
+    return E_UNEXPECTED;
+  }
+
+  RefPtr<IUnknown> originalInterface;
+  HRESULT hr =
+      mGitCookie->GetInterface(mIid, getter_AddRefs(originalInterface));
+  if (FAILED(hr)) {
+    return hr;
+  }
+
+  if (aIid == mIid) {
+    originalInterface.forget(aOutInterface);
+    return S_OK;
+  }
+
+  // ...Whereas the GIT requires us to obtain the same interface that we
+  // requested and then QI for the desired interface afterward.
+  return originalInterface->QueryInterface(aIid, aOutInterface);
+}
+
+}  // namespace mscom
+}  // namespace mozilla
diff --git a/ipc/mscom/AgileReference.h b/ipc/mscom/AgileReference.h
new file mode 100644
index 0000000000..d39e444494
--- /dev/null
+++ b/ipc/mscom/AgileReference.h
@@ -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/. */
+
+#ifndef mozilla_mscom_AgileReference_h
+#define mozilla_mscom_AgileReference_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/RefPtr.h"
+#include "nsISupportsImpl.h"
+
+#include <objidl.h>
+
+namespace mozilla {
+namespace mscom {
+namespace detail {
+
+class MOZ_HEAP_CLASS GlobalInterfaceTableCookie final {
+ public:
+  GlobalInterfaceTableCookie(IUnknown* aObject, REFIID aIid,
+                             HRESULT& aOutHResult);
+
+  bool IsValid() const { return !!mCookie; }
+  HRESULT GetInterface(REFIID aIid, void** aOutInterface) const;
+
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(GlobalInterfaceTableCookie)
+
+  GlobalInterfaceTableCookie(const GlobalInterfaceTableCookie&) = delete;
+  GlobalInterfaceTableCookie(GlobalInterfaceTableCookie&&) = delete;
+
+  GlobalInterfaceTableCookie& operator=(const GlobalInterfaceTableCookie&) =
+      delete;
+  GlobalInterfaceTableCookie& operator=(GlobalInterfaceTableCookie&&) = delete;
+
+ private:
+  ~GlobalInterfaceTableCookie();
+
+ private:
+  DWORD mCookie;
+
+ private:
+  static IGlobalInterfaceTable* ObtainGit();
+};
+
+}  // namespace detail
+
+/**
+ * This class encapsulates an "agile reference." These are references that
+ * allow you to pass COM interfaces between apartments. When you have an
+ * interface that you would like to pass between apartments, you wrap that
+ * interface in an AgileReference and pass the agile reference instead. Then
+ * you unwrap the interface by calling AgileReference::Resolve.
+ *
+ * Sample usage:
+ *
+ * // In the multithreaded apartment, foo is an IFoo*
+ * auto myAgileRef = MakeUnique<AgileReference>(IID_IFoo, foo);
+ *
+ * // myAgileRef is passed to our main thread, which runs in a single-threaded
+ * // apartment:
+ *
+ * RefPtr<IFoo> foo;
+ * HRESULT hr = myAgileRef->Resolve(IID_IFoo, getter_AddRefs(foo));
+ * // Now foo may be called from the main thread
+ */
+class AgileReference final {
+ public:
+  AgileReference();
+
+  template <typename InterfaceT>
+  explicit AgileReference(RefPtr<InterfaceT>& aObject)
+      : AgileReference(__uuidof(InterfaceT), aObject) {}
+
+  AgileReference(REFIID aIid, IUnknown* aObject);
+
+  AgileReference(const AgileReference& aOther) = default;
+  AgileReference(AgileReference&& aOther);
+
+  ~AgileReference();
+
+  explicit operator bool() const {
+    return mAgileRef || (mGitCookie && mGitCookie->IsValid());
+  }
+
+  HRESULT GetHResult() const { return mHResult; }
+
+  template <typename T>
+  void Assign(const RefPtr<T>& aOther) {
+    Assign(__uuidof(T), aOther);
+  }
+
+  template <typename T>
+  AgileReference& operator=(const RefPtr<T>& aOther) {
+    Assign(aOther);
+    return *this;
+  }
+
+  HRESULT Resolve(REFIID aIid, void** aOutInterface) const;
+
+  AgileReference& operator=(const AgileReference& aOther);
+  AgileReference& operator=(AgileReference&& aOther);
+
+  AgileReference& operator=(decltype(nullptr)) {
+    Clear();
+    return *this;
+  }
+
+  void Clear();
+
+ private:
+  void Assign(REFIID aIid, IUnknown* aObject);
+  void AssignInternal(IUnknown* aObject);
+
+ private:
+  IID mIid;
+  RefPtr<IAgileReference> mAgileRef;
+  RefPtr<detail::GlobalInterfaceTableCookie> mGitCookie;
+  HRESULT mHResult;
+};
+
+}  // namespace mscom
+}  // namespace mozilla
+
+template <typename T>
+RefPtr<T>::RefPtr(const mozilla::mscom::AgileReference& aAgileRef)
+    : mRawPtr(nullptr) {
+  (*this) = aAgileRef;
+}
+
+template <typename T>
+RefPtr<T>& RefPtr<T>::operator=(
+    const mozilla::mscom::AgileReference& aAgileRef) {
+  void* newRawPtr;
+  if (FAILED(aAgileRef.Resolve(__uuidof(T), &newRawPtr))) {
+    newRawPtr = nullptr;
+  }
+  assign_assuming_AddRef(static_cast<T*>(newRawPtr));
+  return *this;
+}
+
+#endif  // mozilla_mscom_AgileReference_h
diff --git a/ipc/mscom/ApartmentRegion.h b/ipc/mscom/ApartmentRegion.h
new file mode 100644
index 0000000000..41915710df
--- /dev/null
+++ b/ipc/mscom/ApartmentRegion.h
@@ -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/. */
+
+#ifndef mozilla_mscom_ApartmentRegion_h
+#define mozilla_mscom_ApartmentRegion_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/mscom/COMWrappers.h"
+
+namespace mozilla {
+namespace mscom {
+
+class MOZ_NON_TEMPORARY_CLASS ApartmentRegion final {
+ public:
+  /**
+   * This constructor is to be used when we want to instantiate the object but
+   * we do not yet know which type of apartment we want. Call Init() to
+   * complete initialization.
+   */
+  constexpr ApartmentRegion() : mInitResult(CO_E_NOTINITIALIZED) {}
+
+  explicit ApartmentRegion(COINIT aAptType)
+      : mInitResult(wrapped::CoInitializeEx(nullptr, aAptType)) {
+    // If this fires then we're probably mixing apartments on the same thread
+    MOZ_ASSERT(IsValid());
+  }
+
+  ~ApartmentRegion() {
+    if (IsValid()) {
+      wrapped::CoUninitialize();
+    }
+  }
+
+  explicit operator bool() const { return IsValid(); }
+
+  bool IsValidOutermost() const { return mInitResult == S_OK; }
+
+  bool IsValid() const { return SUCCEEDED(mInitResult); }
+
+  bool Init(COINIT aAptType) {
+    MOZ_ASSERT(mInitResult == CO_E_NOTINITIALIZED);
+    mInitResult = wrapped::CoInitializeEx(nullptr, aAptType);
+    MOZ_ASSERT(IsValid());
+    return IsValid();
+  }
+
+  HRESULT
+  GetHResult() const { return mInitResult; }
+
+ private:
+  ApartmentRegion(const ApartmentRegion&) = delete;
+  ApartmentRegion& operator=(const ApartmentRegion&) = delete;
+  ApartmentRegion(ApartmentRegion&&) = delete;
+  ApartmentRegion& operator=(ApartmentRegion&&) = delete;
+
+  HRESULT mInitResult;
+};
+
+template <COINIT T>
+class MOZ_NON_TEMPORARY_CLASS ApartmentRegionT final {
+ public:
+  ApartmentRegionT() : mAptRgn(T) {}
+
+  ~ApartmentRegionT() = default;
+
+  explicit operator bool() const { return mAptRgn.IsValid(); }
+
+  bool IsValidOutermost() const { return mAptRgn.IsValidOutermost(); }
+
+  bool IsValid() const { return mAptRgn.IsValid(); }
+
+  HRESULT GetHResult() const { return mAptRgn.GetHResult(); }
+
+ private:
+  ApartmentRegionT(const ApartmentRegionT&) = delete;
+  ApartmentRegionT& operator=(const ApartmentRegionT&) = delete;
+  ApartmentRegionT(ApartmentRegionT&&) = delete;
+  ApartmentRegionT& operator=(ApartmentRegionT&&) = delete;
+
+  ApartmentRegion mAptRgn;
+};
+
+typedef ApartmentRegionT<COINIT_APARTMENTTHREADED> STARegion;
+typedef ApartmentRegionT<COINIT_MULTITHREADED> MTARegion;
+
+}  // namespace mscom
+}  // namespace mozilla
+
+#endif  // mozilla_mscom_ApartmentRegion_h
diff --git a/ipc/mscom/COMWrappers.cpp b/ipc/mscom/COMWrappers.cpp
new file mode 100644
index 0000000000..1bc48a4927
--- /dev/null
+++ b/ipc/mscom/COMWrappers.cpp
@@ -0,0 +1,101 @@
+/* -*- 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/mscom/COMWrappers.h"
+
+#include <objbase.h>
+
+#include "mozilla/Assertions.h"
+#include "mozilla/DynamicallyLinkedFunctionPtr.h"
+
+namespace mozilla::mscom::wrapped {
+
+HRESULT CoInitializeEx(LPVOID pvReserved, DWORD dwCoInit) {
+  static const StaticDynamicallyLinkedFunctionPtr<decltype(&::CoInitializeEx)>
+      pCoInitializeEx(L"combase.dll", "CoInitializeEx");
+  if (!pCoInitializeEx) {
+    return ::CoInitializeEx(pvReserved, dwCoInit);
+  }
+
+  return pCoInitializeEx(pvReserved, dwCoInit);
+}
+
+void CoUninitialize() {
+  static const StaticDynamicallyLinkedFunctionPtr<decltype(&::CoUninitialize)>
+      pCoUninitialize(L"combase.dll", "CoUninitialize");
+  if (!pCoUninitialize) {
+    return ::CoUninitialize();
+  }
+
+  return pCoUninitialize();
+}
+
+HRESULT CoIncrementMTAUsage(CO_MTA_USAGE_COOKIE* pCookie) {
+  static const StaticDynamicallyLinkedFunctionPtr<
+      decltype(&::CoIncrementMTAUsage)>
+      pCoIncrementMTAUsage(L"combase.dll", "CoIncrementMTAUsage");
+  // This API is only available beginning with Windows 8.
+  if (!pCoIncrementMTAUsage) {
+    return E_NOTIMPL;
+  }
+
+  HRESULT hr = pCoIncrementMTAUsage(pCookie);
+  MOZ_ASSERT(SUCCEEDED(hr));
+  return hr;
+}
+
+HRESULT CoGetApartmentType(APTTYPE* pAptType, APTTYPEQUALIFIER* pAptQualifier) {
+  static const StaticDynamicallyLinkedFunctionPtr<
+      decltype(&::CoGetApartmentType)>
+      pCoGetApartmentType(L"combase.dll", "CoGetApartmentType");
+  if (!pCoGetApartmentType) {
+    return ::CoGetApartmentType(pAptType, pAptQualifier);
+  }
+
+  return pCoGetApartmentType(pAptType, pAptQualifier);
+}
+
+HRESULT CoInitializeSecurity(PSECURITY_DESCRIPTOR pSecDesc, LONG cAuthSvc,
+                             SOLE_AUTHENTICATION_SERVICE* asAuthSvc,
+                             void* pReserved1, DWORD dwAuthnLevel,
+                             DWORD dwImpLevel, void* pAuthList,
+                             DWORD dwCapabilities, void* pReserved3) {
+  static const StaticDynamicallyLinkedFunctionPtr<
+      decltype(&::CoInitializeSecurity)>
+      pCoInitializeSecurity(L"combase.dll", "CoInitializeSecurity");
+  if (!pCoInitializeSecurity) {
+    return ::CoInitializeSecurity(pSecDesc, cAuthSvc, asAuthSvc, pReserved1,
+                                  dwAuthnLevel, dwImpLevel, pAuthList,
+                                  dwCapabilities, pReserved3);
+  }
+
+  return pCoInitializeSecurity(pSecDesc, cAuthSvc, asAuthSvc, pReserved1,
+                               dwAuthnLevel, dwImpLevel, pAuthList,
+                               dwCapabilities, pReserved3);
+}
+
+HRESULT CoCreateInstance(REFCLSID rclsid, LPUNKNOWN pUnkOuter,
+                         DWORD dwClsContext, REFIID riid, LPVOID* ppv) {
+  static const StaticDynamicallyLinkedFunctionPtr<decltype(&::CoCreateInstance)>
+      pCoCreateInstance(L"combase.dll", "CoCreateInstance");
+  if (!pCoCreateInstance) {
+    return ::CoCreateInstance(rclsid, pUnkOuter, dwClsContext, riid, ppv);
+  }
+
+  return pCoCreateInstance(rclsid, pUnkOuter, dwClsContext, riid, ppv);
+}
+
+HRESULT CoCreateGuid(GUID* pguid) {
+  static const StaticDynamicallyLinkedFunctionPtr<decltype(&::CoCreateGuid)>
+      pCoCreateGuid(L"combase.dll", "CoCreateGuid");
+  if (!pCoCreateGuid) {
+    return ::CoCreateGuid(pguid);
+  }
+
+  return pCoCreateGuid(pguid);
+}
+
+}  // namespace mozilla::mscom::wrapped
diff --git a/ipc/mscom/COMWrappers.h b/ipc/mscom/COMWrappers.h
new file mode 100644
index 0000000000..38bef10749
--- /dev/null
+++ b/ipc/mscom/COMWrappers.h
@@ -0,0 +1,44 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_mscom_COMWrappers_h
+#define mozilla_mscom_COMWrappers_h
+
+#include <objbase.h>
+
+#if (NTDDI_VERSION < NTDDI_WIN8)
+// Win8+ API that we use very carefully
+DECLARE_HANDLE(CO_MTA_USAGE_COOKIE);
+HRESULT WINAPI CoIncrementMTAUsage(CO_MTA_USAGE_COOKIE* pCookie);
+#endif  // (NTDDI_VERSION < NTDDI_WIN8)
+
+// A set of wrapped COM functions, so that we can dynamically link to the
+// functions in combase.dll on win8+. This prevents ole32.dll and many other
+// DLLs loading, which are not required when we have win32k locked down.
+namespace mozilla::mscom::wrapped {
+
+HRESULT CoInitializeEx(LPVOID pvReserved, DWORD dwCoInit);
+
+void CoUninitialize();
+
+HRESULT CoIncrementMTAUsage(CO_MTA_USAGE_COOKIE* pCookie);
+
+HRESULT CoGetApartmentType(APTTYPE* pAptType, APTTYPEQUALIFIER* pAptQualifier);
+
+HRESULT CoInitializeSecurity(PSECURITY_DESCRIPTOR pSecDesc, LONG cAuthSvc,
+                             SOLE_AUTHENTICATION_SERVICE* asAuthSvc,
+                             void* pReserved1, DWORD dwAuthnLevel,
+                             DWORD dwImpLevel, void* pAuthList,
+                             DWORD dwCapabilities, void* pReserved3);
+
+HRESULT CoCreateInstance(REFCLSID rclsid, LPUNKNOWN pUnkOuter,
+                         DWORD dwClsContext, REFIID riid, LPVOID* ppv);
+
+HRESULT CoCreateGuid(GUID* pguid);
+
+}  // namespace mozilla::mscom::wrapped
+
+#endif  // mozilla_mscom_COMWrappers_h
diff --git a/ipc/mscom/EnsureMTA.cpp b/ipc/mscom/EnsureMTA.cpp
new file mode 100644
index 0000000000..0a84eeabf9
--- /dev/null
+++ b/ipc/mscom/EnsureMTA.cpp
@@ -0,0 +1,250 @@
+/* -*- 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/mscom/EnsureMTA.h"
+
+#include "mozilla/Assertions.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/mscom/COMWrappers.h"
+#include "mozilla/mscom/ProcessRuntime.h"
+#include "mozilla/mscom/Utils.h"
+#include "mozilla/SchedulerGroup.h"
+#include "mozilla/StaticLocalPtr.h"
+#include "nsThreadManager.h"
+#include "nsThreadUtils.h"
+
+#include "private/pprthred.h"
+
+namespace {
+
+class EnterMTARunnable : public mozilla::Runnable {
+ public:
+  EnterMTARunnable() : mozilla::Runnable("EnterMTARunnable") {}
+  NS_IMETHOD Run() override {
+    mozilla::DebugOnly<HRESULT> hr =
+        mozilla::mscom::wrapped::CoInitializeEx(nullptr, COINIT_MULTITHREADED);
+    MOZ_ASSERT(SUCCEEDED(hr));
+    return NS_OK;
+  }
+};
+
+class BackgroundMTAData {
+ public:
+  BackgroundMTAData() {
+    nsCOMPtr<nsIRunnable> runnable = new EnterMTARunnable();
+    mozilla::DebugOnly<nsresult> rv = NS_NewNamedThread(
+        "COM MTA", getter_AddRefs(mThread), runnable.forget());
+    NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "NS_NewNamedThread failed");
+    MOZ_ASSERT(NS_SUCCEEDED(rv));
+  }
+
+  ~BackgroundMTAData() {
+    if (mThread) {
+      mThread->Dispatch(
+          NS_NewRunnableFunction("BackgroundMTAData::~BackgroundMTAData",
+                                 &mozilla::mscom::wrapped::CoUninitialize),
+          NS_DISPATCH_NORMAL);
+      mThread->Shutdown();
+    }
+  }
+
+  nsCOMPtr<nsIThread> GetThread() const { return mThread; }
+
+ private:
+  nsCOMPtr<nsIThread> mThread;
+};
+
+}  // anonymous namespace
+
+namespace mozilla {
+namespace mscom {
+
+EnsureMTA::EnsureMTA() {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // It is possible that we're running so early that we might need to start
+  // the thread manager ourselves. We do this here to guarantee that we have
+  // the ability to start the persistent MTA thread at any moment beyond this
+  // point.
+  nsresult rv = nsThreadManager::get().Init();
+  // We intentionally don't check rv unless we need it when
+  // CoIncremementMTAUsage is unavailable.
+
+  // Calling this function initializes the MTA without needing to explicitly
+  // create a thread and call CoInitializeEx to do it.
+  // We don't retain the cookie because once we've incremented the MTA, we
+  // leave it that way for the lifetime of the process.
+  CO_MTA_USAGE_COOKIE mtaCookie = nullptr;
+  HRESULT hr = wrapped::CoIncrementMTAUsage(&mtaCookie);
+  if (SUCCEEDED(hr)) {
+    if (NS_SUCCEEDED(rv)) {
+      // Start the persistent MTA thread (mostly) asynchronously.
+      Unused << GetPersistentMTAThread();
+    }
+
+    return;
+  }
+
+  // In the fallback case, we simply initialize our persistent MTA thread.
+
+  // Make sure thread manager init succeeded before trying to initialize the
+  // persistent MTA thread.
+  MOZ_DIAGNOSTIC_ASSERT(NS_SUCCEEDED(rv));
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  // Before proceeding any further, pump a runnable through the persistent MTA
+  // thread to ensure that it is up and running and has finished initializing
+  // the multi-threaded apartment.
+  nsCOMPtr<nsIRunnable> runnable(NS_NewRunnableFunction(
+      "EnsureMTA::EnsureMTA()",
+      []() { MOZ_RELEASE_ASSERT(IsCurrentThreadExplicitMTA()); }));
+  SyncDispatchToPersistentThread(runnable);
+}
+
+/* static */
+RefPtr<EnsureMTA::CreateInstanceAgileRefPromise>
+EnsureMTA::CreateInstanceInternal(REFCLSID aClsid, REFIID aIid) {
+  MOZ_ASSERT(IsCurrentThreadExplicitMTA());
+
+  RefPtr<IUnknown> iface;
+  HRESULT hr = wrapped::CoCreateInstance(aClsid, nullptr, CLSCTX_INPROC_SERVER,
+                                         aIid, getter_AddRefs(iface));
+  if (FAILED(hr)) {
+    return CreateInstanceAgileRefPromise::CreateAndReject(hr, __func__);
+  }
+
+  // We need to use the two argument constructor for AgileReference because our
+  // RefPtr is not parameterized on the specific interface being requested.
+  AgileReference agileRef(aIid, iface);
+  if (!agileRef) {
+    return CreateInstanceAgileRefPromise::CreateAndReject(agileRef.GetHResult(),
+                                                          __func__);
+  }
+
+  return CreateInstanceAgileRefPromise::CreateAndResolve(std::move(agileRef),
+                                                         __func__);
+}
+
+/* static */
+RefPtr<EnsureMTA::CreateInstanceAgileRefPromise> EnsureMTA::CreateInstance(
+    REFCLSID aClsid, REFIID aIid) {
+  MOZ_ASSERT(IsCOMInitializedOnCurrentThread());
+
+  const bool isClassOk = IsClassThreadAwareInprocServer(aClsid);
+  MOZ_ASSERT(isClassOk,
+             "mozilla::mscom::EnsureMTA::CreateInstance is not "
+             "safe/performant/necessary to use with this CLSID. This CLSID "
+             "either does not support creation from within a multithreaded "
+             "apartment, or it is not an in-process server.");
+  if (!isClassOk) {
+    return CreateInstanceAgileRefPromise::CreateAndReject(CO_E_NOT_SUPPORTED,
+                                                          __func__);
+  }
+
+  if (IsCurrentThreadExplicitMTA()) {
+    // It's safe to immediately call CreateInstanceInternal
+    return CreateInstanceInternal(aClsid, aIid);
+  }
+
+  // aClsid and aIid are references. Make local copies that we can put into the
+  // lambda in case the sources of aClsid or aIid are not static data
+  CLSID localClsid = aClsid;
+  IID localIid = aIid;
+
+  auto invoker = [localClsid,
+                  localIid]() -> RefPtr<CreateInstanceAgileRefPromise> {
+    return CreateInstanceInternal(localClsid, localIid);
+  };
+
+  nsCOMPtr<nsIThread> mtaThread(GetPersistentMTAThread());
+
+  return InvokeAsync(mtaThread, __func__, std::move(invoker));
+}
+
+/* static */
+nsCOMPtr<nsIThread> EnsureMTA::GetPersistentMTAThread() {
+  static StaticLocalAutoPtr<BackgroundMTAData> sMTAData(
+      []() -> BackgroundMTAData* {
+        BackgroundMTAData* bgData = new BackgroundMTAData();
+
+        auto setClearOnShutdown = [ptr = &sMTAData]() -> void {
+          ClearOnShutdown(ptr, ShutdownPhase::XPCOMShutdownThreads);
+        };
+
+        if (NS_IsMainThread()) {
+          setClearOnShutdown();
+          return bgData;
+        }
+
+        SchedulerGroup::Dispatch(
+            TaskCategory::Other,
+            NS_NewRunnableFunction("mscom::EnsureMTA::GetPersistentMTAThread",
+                                   std::move(setClearOnShutdown)));
+
+        return bgData;
+      }());
+
+  MOZ_ASSERT(sMTAData);
+
+  return sMTAData->GetThread();
+}
+
+/* static */
+void EnsureMTA::SyncDispatchToPersistentThread(nsIRunnable* aRunnable) {
+  nsCOMPtr<nsIThread> thread(GetPersistentMTAThread());
+  MOZ_ASSERT(thread);
+  if (!thread) {
+    return;
+  }
+
+  // Note that, due to APC dispatch, we might reenter this function while we
+  // wait on this event. We therefore need a unique event object for each
+  // entry into this function. If perf becomes an issue then we will want to
+  // maintain an array of events where the Nth event is unique to the Nth
+  // reentry.
+  nsAutoHandle event(::CreateEventW(nullptr, FALSE, FALSE, nullptr));
+  if (!event) {
+    return;
+  }
+
+  HANDLE eventHandle = event.get();
+  auto eventSetter = [&aRunnable, eventHandle]() -> void {
+    aRunnable->Run();
+    ::SetEvent(eventHandle);
+  };
+
+  nsresult rv = thread->Dispatch(
+      NS_NewRunnableFunction("mscom::EnsureMTA::SyncDispatchToPersistentThread",
+                             std::move(eventSetter)),
+      NS_DISPATCH_NORMAL);
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  AUTO_PROFILER_THREAD_SLEEP;
+  DWORD waitResult;
+  while ((waitResult = ::WaitForSingleObjectEx(event, INFINITE, FALSE)) ==
+         WAIT_IO_COMPLETION) {
+  }
+  MOZ_ASSERT(waitResult == WAIT_OBJECT_0);
+}
+
+/**
+ * While this function currently appears to be redundant, it may become more
+ * sophisticated in the future. For example, we could optionally dispatch to an
+ * MTA context if we wanted to utilize the MTA thread pool.
+ */
+/* static */
+void EnsureMTA::SyncDispatch(nsCOMPtr<nsIRunnable>&& aRunnable, Option aOpt) {
+  SyncDispatchToPersistentThread(aRunnable);
+}
+
+}  // namespace mscom
+}  // namespace mozilla
diff --git a/ipc/mscom/EnsureMTA.h b/ipc/mscom/EnsureMTA.h
new file mode 100644
index 0000000000..5e410d4daa
--- /dev/null
+++ b/ipc/mscom/EnsureMTA.h
@@ -0,0 +1,191 @@
+/* -*- 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_mscom_EnsureMTA_h
+#define mozilla_mscom_EnsureMTA_h
+
+#include "MainThreadUtils.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/MozPromise.h"
+#include "mozilla/Unused.h"
+#include "mozilla/mscom/AgileReference.h"
+#include "mozilla/mscom/Utils.h"
+#include "mozilla/RefPtr.h"
+#include "nsCOMPtr.h"
+#include "nsIThread.h"
+#include "nsThreadUtils.h"
+#include "nsWindowsHelpers.h"
+
+#include <windows.h>
+
+namespace mozilla {
+namespace mscom {
+namespace detail {
+
+// Forward declarations
+template <typename T>
+struct MTADelete;
+
+template <typename T>
+struct MTARelease;
+
+template <typename T>
+struct MTAReleaseInChildProcess;
+
+struct PreservedStreamDeleter;
+
+}  // namespace detail
+
+class ProcessRuntime;
+
+// This class is OK to use as a temporary on the stack.
+class MOZ_STACK_CLASS EnsureMTA final {
+ public:
+  enum class Option {
+    Default,
+    // Forcibly dispatch to the thread returned by GetPersistentMTAThread(),
+    // even if the current thread is already inside a MTA.
+    ForceDispatchToPersistentThread,
+  };
+
+  /**
+   * Synchronously run |aClosure| on a thread living in the COM multithreaded
+   * apartment. If the current thread lives inside the COM MTA, then it runs
+   * |aClosure| immediately unless |aOpt| ==
+   * Option::ForceDispatchToPersistentThread.
+   */
+  template <typename FuncT>
+  explicit EnsureMTA(FuncT&& aClosure, Option aOpt = Option::Default) {
+    if (aOpt != Option::ForceDispatchToPersistentThread &&
+        IsCurrentThreadMTA()) {
+      // We're already on the MTA, we can run aClosure directly
+      aClosure();
+      return;
+    }
+
+    // In this case we need to run aClosure on a background thread in the MTA
+    nsCOMPtr<nsIRunnable> runnable(
+        NS_NewRunnableFunction("EnsureMTA::EnsureMTA", std::move(aClosure)));
+    SyncDispatch(std::move(runnable), aOpt);
+  }
+
+  using CreateInstanceAgileRefPromise =
+      MozPromise<AgileReference, HRESULT, false>;
+
+  /**
+   *       *** A MSCOM PEER SHOULD REVIEW ALL NEW USES OF THIS API! ***
+   *
+   * Asynchronously instantiate a new COM object from a MTA thread, unless the
+   * current thread is already living inside the multithreaded apartment, in
+   * which case the object is immediately instantiated.
+   *
+   * This function only supports the most common configurations for creating
+   * a new object, so it only supports in-process servers. Furthermore, this
+   * function does not support aggregation (ie. the |pUnkOuter| parameter to
+   * CoCreateInstance).
+   *
+   * Given that attempting to instantiate an Apartment-threaded COM object
+   * inside the MTA results in a *loss* of performance, we assert when that
+   * situation arises.
+   *
+   * The resulting promise, once resolved, provides an AgileReference that may
+   * be passed between any COM-initialized thread in the current process.
+   *
+   *       *** A MSCOM PEER SHOULD REVIEW ALL NEW USES OF THIS API! ***
+   *
+   * WARNING:
+   * Some COM objects do not support creation in the multithreaded apartment,
+   * in which case this function is not available as an option. In this case,
+   * the promise will always be rejected. In debug builds we will assert.
+   *
+   *       *** A MSCOM PEER SHOULD REVIEW ALL NEW USES OF THIS API! ***
+   *
+   * WARNING:
+   * Any in-process COM objects whose interfaces accept HWNDs are probably
+   * *not* safe to instantiate in the multithreaded apartment! Even if this
+   * function succeeds when creating such an object, you *MUST NOT* do so, as
+   * these failures might not become apparent until your code is running out in
+   * the wild on the release channel!
+   *
+   *       *** A MSCOM PEER SHOULD REVIEW ALL NEW USES OF THIS API! ***
+   *
+   * WARNING:
+   * When you obtain an interface from the AgileReference, it may or may not be
+   * a proxy to the real object. This depends entirely on the implementation of
+   * the underlying class and the multithreading capabilities that the class
+   * declares to the COM runtime. If the interface is proxied, it might be
+   * expensive to invoke methods on that interface! *Always* test the
+   * performance of your method calls when calling interfaces that are resolved
+   * via this function!
+   *
+   *       *** A MSCOM PEER SHOULD REVIEW ALL NEW USES OF THIS API! ***
+   *
+   * (Despite this myriad of warnings, it is still *much* safer to use this
+   * function to asynchronously create COM objects than it is to roll your own!)
+   *
+   *       *** A MSCOM PEER SHOULD REVIEW ALL NEW USES OF THIS API! ***
+   */
+  static RefPtr<CreateInstanceAgileRefPromise> CreateInstance(REFCLSID aClsid,
+                                                              REFIID aIid);
+
+ private:
+  static RefPtr<CreateInstanceAgileRefPromise> CreateInstanceInternal(
+      REFCLSID aClsid, REFIID aIid);
+
+  static nsCOMPtr<nsIThread> GetPersistentMTAThread();
+
+  static void SyncDispatch(nsCOMPtr<nsIRunnable>&& aRunnable, Option aOpt);
+  static void SyncDispatchToPersistentThread(nsIRunnable* aRunnable);
+
+  // The following function is private in order to force any consumers to be
+  // declared as friends of EnsureMTA. The intention is to prevent
+  // AsyncOperation from becoming some kind of free-for-all mechanism for
+  // asynchronously executing work on a background thread.
+  template <typename FuncT>
+  static void AsyncOperation(FuncT&& aClosure) {
+    if (IsCurrentThreadMTA()) {
+      aClosure();
+      return;
+    }
+
+    nsCOMPtr<nsIThread> thread(GetPersistentMTAThread());
+    MOZ_ASSERT(thread);
+    if (!thread) {
+      return;
+    }
+
+    DebugOnly<nsresult> rv = thread->Dispatch(
+        NS_NewRunnableFunction("mscom::EnsureMTA::AsyncOperation",
+                               std::move(aClosure)),
+        NS_DISPATCH_NORMAL);
+    MOZ_ASSERT(NS_SUCCEEDED(rv));
+  }
+
+  /**
+   * This constructor just ensures that the MTA is up and running. This should
+   * only be called by ProcessRuntime.
+   */
+  EnsureMTA();
+
+  friend class mozilla::mscom::ProcessRuntime;
+
+  template <typename T>
+  friend struct mozilla::mscom::detail::MTADelete;
+
+  template <typename T>
+  friend struct mozilla::mscom::detail::MTARelease;
+
+  template <typename T>
+  friend struct mozilla::mscom::detail::MTAReleaseInChildProcess;
+
+  friend struct mozilla::mscom::detail::PreservedStreamDeleter;
+};
+
+}  // namespace mscom
+}  // namespace mozilla
+
+#endif  // mozilla_mscom_EnsureMTA_h
diff --git a/ipc/mscom/ProcessRuntime.cpp b/ipc/mscom/ProcessRuntime.cpp
new file mode 100644
index 0000000000..f20b0658bb
--- /dev/null
+++ b/ipc/mscom/ProcessRuntime.cpp
@@ -0,0 +1,458 @@
+/* -*- 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/mscom/ProcessRuntime.h"
+
+#include "mozilla/Assertions.h"
+#include "mozilla/DynamicallyLinkedFunctionPtr.h"
+#include "mozilla/mscom/COMWrappers.h"
+#include "mozilla/mscom/ProcessRuntimeShared.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/Unused.h"
+#include "mozilla/Vector.h"
+#include "mozilla/WindowsProcessMitigations.h"
+#include "mozilla/WindowsVersion.h"
+
+#if defined(MOZILLA_INTERNAL_API)
+#  include "mozilla/mscom/EnsureMTA.h"
+#  if defined(MOZ_SANDBOX)
+#    include "mozilla/sandboxTarget.h"
+#  endif  // defined(MOZ_SANDBOX)
+#endif    // defined(MOZILLA_INTERNAL_API)
+
+#include <accctrl.h>
+#include <aclapi.h>
+#include <objbase.h>
+#include <objidl.h>
+
+// This API from oleaut32.dll is not declared in Windows SDK headers
+extern "C" void __cdecl SetOaNoCache(void);
+
+using namespace mozilla::mscom::detail;
+
+namespace mozilla {
+namespace mscom {
+
+#if defined(MOZILLA_INTERNAL_API)
+ProcessRuntime* ProcessRuntime::sInstance = nullptr;
+
+ProcessRuntime::ProcessRuntime() : ProcessRuntime(XRE_GetProcessType()) {}
+
+ProcessRuntime::ProcessRuntime(const GeckoProcessType aProcessType)
+    : ProcessRuntime(aProcessType == GeckoProcessType_Default
+                         ? ProcessCategory::GeckoBrowserParent
+                         : ProcessCategory::GeckoChild) {}
+#endif  // defined(MOZILLA_INTERNAL_API)
+
+ProcessRuntime::ProcessRuntime(const ProcessCategory aProcessCategory)
+    : mInitResult(CO_E_NOTINITIALIZED), mProcessCategory(aProcessCategory) {
+#if defined(MOZILLA_INTERNAL_API)
+  MOZ_DIAGNOSTIC_ASSERT(!sInstance);
+  sInstance = this;
+
+  EnsureMTA();
+  /**
+   * From this point forward, all threads in this process are implicitly
+   * members of the multi-threaded apartment, with the following exceptions:
+   * 1. If any Win32 GUI APIs were called on the current thread prior to
+   *    executing this constructor, then this thread has already been implicitly
+   *    initialized as the process's main STA thread; or
+   * 2. A thread explicitly and successfully calls CoInitialize(Ex) to specify
+   *    otherwise.
+   */
+
+  const bool isCurThreadImplicitMTA = IsCurrentThreadImplicitMTA();
+  // We only assert that the implicit MTA precondition holds when not running
+  // as the Gecko parent process.
+  MOZ_DIAGNOSTIC_ASSERT(aProcessCategory ==
+                            ProcessCategory::GeckoBrowserParent ||
+                        isCurThreadImplicitMTA);
+
+#  if defined(MOZ_SANDBOX)
+  const bool isLockedDownChildProcess =
+      mProcessCategory == ProcessCategory::GeckoChild && IsWin32kLockedDown();
+  // If our process is running under Win32k lockdown, we cannot initialize
+  // COM with a single-threaded apartment. This is because STAs create a hidden
+  // window, which implicitly requires user32 and Win32k, which are blocked.
+  // Instead we start the multi-threaded apartment and conduct our process-wide
+  // COM initialization there.
+  if (isLockedDownChildProcess) {
+    // Make sure we're still running with the sandbox's privileged impersonation
+    // token.
+    HANDLE rawCurThreadImpToken;
+    if (!::OpenThreadToken(::GetCurrentThread(), TOKEN_DUPLICATE | TOKEN_QUERY,
+                           FALSE, &rawCurThreadImpToken)) {
+      mInitResult = HRESULT_FROM_WIN32(::GetLastError());
+      return;
+    }
+    nsAutoHandle curThreadImpToken(rawCurThreadImpToken);
+
+    // Ensure that our current token is still an impersonation token (ie, we
+    // have not yet called RevertToSelf() on this thread).
+    DWORD len;
+    TOKEN_TYPE tokenType;
+    MOZ_RELEASE_ASSERT(
+        ::GetTokenInformation(rawCurThreadImpToken, TokenType, &tokenType,
+                              sizeof(tokenType), &len) &&
+        len == sizeof(tokenType) && tokenType == TokenImpersonation);
+
+    // Ideally we want our current thread to be running implicitly inside the
+    // MTA, but if for some wacky reason we did not end up with that, we may
+    // compensate by completing initialization via EnsureMTA's persistent
+    // thread.
+    if (!isCurThreadImplicitMTA) {
+      InitUsingPersistentMTAThread(curThreadImpToken);
+      return;
+    }
+  }
+#  endif  // defined(MOZ_SANDBOX)
+#endif    // defined(MOZILLA_INTERNAL_API)
+
+  mAptRegion.Init(GetDesiredApartmentType(mProcessCategory));
+
+  // It can happen that we are not the outermost COM initialization on this
+  // thread. In fact it should regularly be the case that the outermost
+  // initialization occurs from outside of XUL, before we show the skeleton UI,
+  // at which point we still need to run some things here from within XUL.
+  if (!mAptRegion.IsValidOutermost()) {
+    mInitResult = mAptRegion.GetHResult();
+#if defined(MOZILLA_INTERNAL_API)
+    MOZ_ASSERT(mProcessCategory == ProcessCategory::GeckoBrowserParent);
+    if (mProcessCategory != ProcessCategory::GeckoBrowserParent) {
+      // This is unexpected unless we're GeckoBrowserParent
+      return;
+    }
+
+    ProcessInitLock lock;
+
+    // Is another instance of ProcessRuntime responsible for the outer
+    // initialization?
+    const bool prevInit =
+        lock.GetInitState() == ProcessInitState::FullyInitialized;
+    MOZ_ASSERT(prevInit);
+    if (prevInit) {
+      PostInit();
+    }
+#endif  // defined(MOZILLA_INTERNAL_API)
+    return;
+  }
+
+  InitInsideApartment();
+  if (FAILED(mInitResult)) {
+    return;
+  }
+
+#if defined(MOZILLA_INTERNAL_API)
+#  if defined(MOZ_SANDBOX)
+  if (isLockedDownChildProcess) {
+    // In locked-down child processes, defer PostInit until priv drop
+    SandboxTarget::Instance()->RegisterSandboxStartCallback([self = this]() {
+      // Ensure that we're still live and the init was successful before
+      // calling PostInit()
+      if (self == sInstance && SUCCEEDED(self->mInitResult)) {
+        PostInit();
+      }
+    });
+    return;
+  }
+#  endif  // defined(MOZ_SANDBOX)
+
+  PostInit();
+#endif  // defined(MOZILLA_INTERNAL_API)
+}
+
+#if defined(MOZILLA_INTERNAL_API)
+ProcessRuntime::~ProcessRuntime() {
+  MOZ_DIAGNOSTIC_ASSERT(sInstance == this);
+  sInstance = nullptr;
+}
+
+#  if defined(MOZ_SANDBOX)
+void ProcessRuntime::InitUsingPersistentMTAThread(
+    const nsAutoHandle& aCurThreadToken) {
+  // Create an impersonation token based on the current thread's token
+  HANDLE rawMtaThreadImpToken = nullptr;
+  if (!::DuplicateToken(aCurThreadToken, SecurityImpersonation,
+                        &rawMtaThreadImpToken)) {
+    mInitResult = HRESULT_FROM_WIN32(::GetLastError());
+    return;
+  }
+  nsAutoHandle mtaThreadImpToken(rawMtaThreadImpToken);
+
+  // Impersonate and initialize.
+  bool tokenSet = false;
+  EnsureMTA(
+      [this, rawMtaThreadImpToken, &tokenSet]() -> void {
+        if (!::SetThreadToken(nullptr, rawMtaThreadImpToken)) {
+          mInitResult = HRESULT_FROM_WIN32(::GetLastError());
+          return;
+        }
+
+        tokenSet = true;
+        InitInsideApartment();
+      },
+      EnsureMTA::Option::ForceDispatchToPersistentThread);
+
+  if (!tokenSet) {
+    return;
+  }
+
+  SandboxTarget::Instance()->RegisterSandboxStartCallback(
+      [self = this]() -> void {
+        EnsureMTA(
+            []() -> void {
+              // This is a security risk if it fails, so we release assert
+              MOZ_RELEASE_ASSERT(::RevertToSelf(),
+                                 "mscom::ProcessRuntime RevertToSelf failed");
+            },
+            EnsureMTA::Option::ForceDispatchToPersistentThread);
+
+        // Ensure that we're still live and the init was successful before
+        // calling PostInit()
+        if (self == sInstance && SUCCEEDED(self->mInitResult)) {
+          PostInit();
+        }
+      });
+}
+#  endif  // defined(MOZ_SANDBOX)
+#endif    // defined(MOZILLA_INTERNAL_API)
+
+/* static */
+COINIT ProcessRuntime::GetDesiredApartmentType(
+    const ProcessRuntime::ProcessCategory aProcessCategory) {
+  switch (aProcessCategory) {
+    case ProcessCategory::GeckoBrowserParent:
+      return COINIT_APARTMENTTHREADED;
+    case ProcessCategory::GeckoChild:
+      if (!IsWin32kLockedDown()) {
+        // If Win32k is not locked down then we probably still need STA.
+        // We disable DDE since that is not usable from child processes.
+        return static_cast<COINIT>(COINIT_APARTMENTTHREADED |
+                                   COINIT_DISABLE_OLE1DDE);
+      }
+
+      [[fallthrough]];
+    default:
+      return COINIT_MULTITHREADED;
+  }
+}
+
+void ProcessRuntime::InitInsideApartment() {
+  ProcessInitLock lock;
+  const ProcessInitState prevInitState = lock.GetInitState();
+  if (prevInitState == ProcessInitState::FullyInitialized) {
+    // COM has already been initialized by a previous ProcessRuntime instance
+    mInitResult = S_OK;
+    return;
+  }
+
+  if (prevInitState < ProcessInitState::PartialSecurityInitialized) {
+    // We are required to initialize security prior to configuring global
+    // options.
+    mInitResult = InitializeSecurity(mProcessCategory);
+    MOZ_DIAGNOSTIC_ASSERT(SUCCEEDED(mInitResult));
+
+    // Even though this isn't great, we should try to proceed even when
+    // CoInitializeSecurity has previously been called: the additional settings
+    // we want to change are important enough that we don't want to skip them.
+    if (FAILED(mInitResult) && mInitResult != RPC_E_TOO_LATE) {
+      return;
+    }
+
+    lock.SetInitState(ProcessInitState::PartialSecurityInitialized);
+  }
+
+  if (prevInitState < ProcessInitState::PartialGlobalOptions) {
+    RefPtr<IGlobalOptions> globalOpts;
+    mInitResult = wrapped::CoCreateInstance(
+        CLSID_GlobalOptions, nullptr, CLSCTX_INPROC_SERVER, IID_IGlobalOptions,
+        getter_AddRefs(globalOpts));
+    MOZ_ASSERT(SUCCEEDED(mInitResult));
+    if (FAILED(mInitResult)) {
+      return;
+    }
+
+    // Disable COM's catch-all exception handler
+    mInitResult = globalOpts->Set(COMGLB_EXCEPTION_HANDLING,
+                                  COMGLB_EXCEPTION_DONOT_HANDLE_ANY);
+    MOZ_ASSERT(SUCCEEDED(mInitResult));
+    if (FAILED(mInitResult)) {
+      return;
+    }
+
+    lock.SetInitState(ProcessInitState::PartialGlobalOptions);
+  }
+
+  // Disable the BSTR cache (as it never invalidates, thus leaking memory)
+  // (This function is itself idempotent, so we do not concern ourselves with
+  // tracking whether or not we've already called it.)
+  ::SetOaNoCache();
+
+  lock.SetInitState(ProcessInitState::FullyInitialized);
+}
+
+#if defined(MOZILLA_INTERNAL_API)
+/**
+ * Guaranteed to run *after* the COM (and possible sandboxing) initialization
+ * has successfully completed and stabilized. This method MUST BE IDEMPOTENT!
+ */
+/* static */ void ProcessRuntime::PostInit() {
+  // Currently "roughed-in" but unused.
+}
+#endif  // defined(MOZILLA_INTERNAL_API)
+
+/* static */
+DWORD
+ProcessRuntime::GetClientThreadId() {
+  DWORD callerTid;
+  HRESULT hr = ::CoGetCallerTID(&callerTid);
+  // Don't return callerTid unless the call succeeded and returned S_FALSE,
+  // indicating that the caller originates from a different process.
+  if (hr != S_FALSE) {
+    return 0;
+  }
+
+  return callerTid;
+}
+
+/* static */
+HRESULT
+ProcessRuntime::InitializeSecurity(const ProcessCategory aProcessCategory) {
+  HANDLE rawToken = nullptr;
+  BOOL ok = ::OpenProcessToken(::GetCurrentProcess(), TOKEN_QUERY, &rawToken);
+  if (!ok) {
+    return HRESULT_FROM_WIN32(::GetLastError());
+  }
+  nsAutoHandle token(rawToken);
+
+  DWORD len = 0;
+  ok = ::GetTokenInformation(token, TokenUser, nullptr, len, &len);
+  DWORD win32Error = ::GetLastError();
+  if (!ok && win32Error != ERROR_INSUFFICIENT_BUFFER) {
+    return HRESULT_FROM_WIN32(win32Error);
+  }
+
+  auto tokenUserBuf = MakeUnique<BYTE[]>(len);
+  TOKEN_USER& tokenUser = *reinterpret_cast<TOKEN_USER*>(tokenUserBuf.get());
+  ok = ::GetTokenInformation(token, TokenUser, tokenUserBuf.get(), len, &len);
+  if (!ok) {
+    return HRESULT_FROM_WIN32(::GetLastError());
+  }
+
+  len = 0;
+  ok = ::GetTokenInformation(token, TokenPrimaryGroup, nullptr, len, &len);
+  win32Error = ::GetLastError();
+  if (!ok && win32Error != ERROR_INSUFFICIENT_BUFFER) {
+    return HRESULT_FROM_WIN32(win32Error);
+  }
+
+  auto tokenPrimaryGroupBuf = MakeUnique<BYTE[]>(len);
+  TOKEN_PRIMARY_GROUP& tokenPrimaryGroup =
+      *reinterpret_cast<TOKEN_PRIMARY_GROUP*>(tokenPrimaryGroupBuf.get());
+  ok = ::GetTokenInformation(token, TokenPrimaryGroup,
+                             tokenPrimaryGroupBuf.get(), len, &len);
+  if (!ok) {
+    return HRESULT_FROM_WIN32(::GetLastError());
+  }
+
+  SECURITY_DESCRIPTOR sd;
+  if (!::InitializeSecurityDescriptor(&sd, SECURITY_DESCRIPTOR_REVISION)) {
+    return HRESULT_FROM_WIN32(::GetLastError());
+  }
+
+  BYTE systemSid[SECURITY_MAX_SID_SIZE];
+  DWORD systemSidSize = sizeof(systemSid);
+  if (!::CreateWellKnownSid(WinLocalSystemSid, nullptr, systemSid,
+                            &systemSidSize)) {
+    return HRESULT_FROM_WIN32(::GetLastError());
+  }
+
+  BYTE adminSid[SECURITY_MAX_SID_SIZE];
+  DWORD adminSidSize = sizeof(adminSid);
+  if (!::CreateWellKnownSid(WinBuiltinAdministratorsSid, nullptr, adminSid,
+                            &adminSidSize)) {
+    return HRESULT_FROM_WIN32(::GetLastError());
+  }
+
+  const bool allowAppContainers =
+      aProcessCategory == ProcessCategory::GeckoBrowserParent &&
+      IsWin8OrLater();
+
+  BYTE appContainersSid[SECURITY_MAX_SID_SIZE];
+  DWORD appContainersSidSize = sizeof(appContainersSid);
+  if (allowAppContainers) {
+    if (!::CreateWellKnownSid(WinBuiltinAnyPackageSid, nullptr,
+                              appContainersSid, &appContainersSidSize)) {
+      return HRESULT_FROM_WIN32(::GetLastError());
+    }
+  }
+
+  // Grant access to SYSTEM, Administrators, the user, and when running as the
+  // browser process on Windows 8+, all app containers.
+  const size_t kMaxInlineEntries = 4;
+  mozilla::Vector<EXPLICIT_ACCESS_W, kMaxInlineEntries> entries;
+
+  Unused << entries.append(EXPLICIT_ACCESS_W{
+      COM_RIGHTS_EXECUTE,
+      GRANT_ACCESS,
+      NO_INHERITANCE,
+      {nullptr, NO_MULTIPLE_TRUSTEE, TRUSTEE_IS_SID, TRUSTEE_IS_USER,
+       reinterpret_cast<LPWSTR>(systemSid)}});
+
+  Unused << entries.append(EXPLICIT_ACCESS_W{
+      COM_RIGHTS_EXECUTE,
+      GRANT_ACCESS,
+      NO_INHERITANCE,
+      {nullptr, NO_MULTIPLE_TRUSTEE, TRUSTEE_IS_SID,
+       TRUSTEE_IS_WELL_KNOWN_GROUP, reinterpret_cast<LPWSTR>(adminSid)}});
+
+  Unused << entries.append(EXPLICIT_ACCESS_W{
+      COM_RIGHTS_EXECUTE,
+      GRANT_ACCESS,
+      NO_INHERITANCE,
+      {nullptr, NO_MULTIPLE_TRUSTEE, TRUSTEE_IS_SID, TRUSTEE_IS_USER,
+       reinterpret_cast<LPWSTR>(tokenUser.User.Sid)}});
+
+  if (allowAppContainers) {
+    Unused << entries.append(
+        EXPLICIT_ACCESS_W{COM_RIGHTS_EXECUTE,
+                          GRANT_ACCESS,
+                          NO_INHERITANCE,
+                          {nullptr, NO_MULTIPLE_TRUSTEE, TRUSTEE_IS_SID,
+                           TRUSTEE_IS_WELL_KNOWN_GROUP,
+                           reinterpret_cast<LPWSTR>(appContainersSid)}});
+  }
+
+  PACL rawDacl = nullptr;
+  win32Error =
+      ::SetEntriesInAclW(entries.length(), entries.begin(), nullptr, &rawDacl);
+  if (win32Error != ERROR_SUCCESS) {
+    return HRESULT_FROM_WIN32(win32Error);
+  }
+
+  UniquePtr<ACL, LocalFreeDeleter> dacl(rawDacl);
+
+  if (!::SetSecurityDescriptorDacl(&sd, TRUE, dacl.get(), FALSE)) {
+    return HRESULT_FROM_WIN32(::GetLastError());
+  }
+
+  if (!::SetSecurityDescriptorOwner(&sd, tokenUser.User.Sid, FALSE)) {
+    return HRESULT_FROM_WIN32(::GetLastError());
+  }
+
+  if (!::SetSecurityDescriptorGroup(&sd, tokenPrimaryGroup.PrimaryGroup,
+                                    FALSE)) {
+    return HRESULT_FROM_WIN32(::GetLastError());
+  }
+
+  return wrapped::CoInitializeSecurity(
+      &sd, -1, nullptr, nullptr, RPC_C_AUTHN_LEVEL_DEFAULT,
+      RPC_C_IMP_LEVEL_IDENTIFY, nullptr, EOAC_NONE, nullptr);
+}
+
+}  // namespace mscom
+}  // namespace mozilla
diff --git a/ipc/mscom/ProcessRuntime.h b/ipc/mscom/ProcessRuntime.h
new file mode 100644
index 0000000000..568281f360
--- /dev/null
+++ b/ipc/mscom/ProcessRuntime.h
@@ -0,0 +1,87 @@
+/* -*- 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_mscom_ProcessRuntime_h
+#define mozilla_mscom_ProcessRuntime_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/mscom/ApartmentRegion.h"
+#include "nsWindowsHelpers.h"
+#if defined(MOZILLA_INTERNAL_API)
+#  include "nsXULAppAPI.h"
+#endif  // defined(MOZILLA_INTERNAL_API)
+
+namespace mozilla {
+namespace mscom {
+
+class MOZ_NON_TEMPORARY_CLASS ProcessRuntime final {
+#if !defined(MOZILLA_INTERNAL_API)
+ public:
+#endif  // defined(MOZILLA_INTERNAL_API)
+  enum class ProcessCategory {
+    GeckoBrowserParent,
+    // We give Launcher its own process category, but internally to this class
+    // it should be treated identically to GeckoBrowserParent.
+    Launcher = GeckoBrowserParent,
+    GeckoChild,
+    Service,
+  };
+
+  // This constructor is only public when compiled outside of XUL
+  explicit ProcessRuntime(const ProcessCategory aProcessCategory);
+
+ public:
+#if defined(MOZILLA_INTERNAL_API)
+  ProcessRuntime();
+  ~ProcessRuntime();
+#else
+  ~ProcessRuntime() = default;
+#endif  // defined(MOZILLA_INTERNAL_API)
+
+  explicit operator bool() const { return SUCCEEDED(mInitResult); }
+  HRESULT GetHResult() const { return mInitResult; }
+
+  ProcessRuntime(const ProcessRuntime&) = delete;
+  ProcessRuntime(ProcessRuntime&&) = delete;
+  ProcessRuntime& operator=(const ProcessRuntime&) = delete;
+  ProcessRuntime& operator=(ProcessRuntime&&) = delete;
+
+  /**
+   * @return 0 if call is in-process or resolving the calling thread failed,
+   *         otherwise contains the thread id of the calling thread.
+   */
+  static DWORD GetClientThreadId();
+
+ private:
+#if defined(MOZILLA_INTERNAL_API)
+  explicit ProcessRuntime(const GeckoProcessType aProcessType);
+#  if defined(MOZ_SANDBOX)
+  void InitUsingPersistentMTAThread(const nsAutoHandle& aCurThreadToken);
+#  endif  // defined(MOZ_SANDBOX)
+#endif    // defined(MOZILLA_INTERNAL_API)
+  void InitInsideApartment();
+
+#if defined(MOZILLA_INTERNAL_API)
+  static void PostInit();
+#endif  // defined(MOZILLA_INTERNAL_API)
+  static HRESULT InitializeSecurity(const ProcessCategory aProcessCategory);
+  static COINIT GetDesiredApartmentType(const ProcessCategory aProcessCategory);
+
+ private:
+  HRESULT mInitResult;
+  const ProcessCategory mProcessCategory;
+  ApartmentRegion mAptRegion;
+
+ private:
+#if defined(MOZILLA_INTERNAL_API)
+  static ProcessRuntime* sInstance;
+#endif  // defined(MOZILLA_INTERNAL_API)
+};
+
+}  // namespace mscom
+}  // namespace mozilla
+
+#endif  // mozilla_mscom_ProcessRuntime_h
diff --git a/ipc/mscom/ProfilerMarkers.cpp b/ipc/mscom/ProfilerMarkers.cpp
new file mode 100644
index 0000000000..29d033723f
--- /dev/null
+++ b/ipc/mscom/ProfilerMarkers.cpp
@@ -0,0 +1,236 @@
+/* -*- 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 "ProfilerMarkers.h"
+
+#include "MainThreadUtils.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/mscom/Utils.h"
+#include "mozilla/ProfilerMarkers.h"
+#include "mozilla/Services.h"
+#include "nsCOMPtr.h"
+#include "nsIObserver.h"
+#include "nsIObserverService.h"
+#include "nsISupportsImpl.h"
+#include "nsString.h"
+#include "nsXULAppAPI.h"
+
+#include <objbase.h>
+#include <objidlbase.h>
+
+// {9DBE6B28-E5E7-4FDE-AF00-9404604E74DC}
+static const GUID GUID_MozProfilerMarkerExtension = {
+    0x9dbe6b28, 0xe5e7, 0x4fde, {0xaf, 0x0, 0x94, 0x4, 0x60, 0x4e, 0x74, 0xdc}};
+
+namespace {
+
+class ProfilerMarkerChannelHook final : public IChannelHook {
+  ~ProfilerMarkerChannelHook() = default;
+
+ public:
+  ProfilerMarkerChannelHook() : mRefCnt(0) {}
+
+  // IUnknown
+  STDMETHODIMP QueryInterface(REFIID aIid, void** aOutInterface) override;
+  STDMETHODIMP_(ULONG) AddRef() override;
+  STDMETHODIMP_(ULONG) Release() override;
+
+  /**
+   * IChannelHook exposes six methods: The Client* methods are called when
+   * a client is sending an IPC request, whereas the Server* methods are called
+   * when a server is receiving an IPC request.
+   *
+   * For our purposes, we only care about the client-side methods. The COM
+   * runtime invokes the methods in the following order:
+   * 1. ClientGetSize, where the hook specifies the size of its payload;
+   * 2. ClientFillBuffer, where the hook fills the channel's buffer with its
+   *    payload information. NOTE: This method is only called when ClientGetSize
+   *    specifies a non-zero payload size. For our purposes, since we are not
+   *    sending a payload, this method will never be called!
+   * 3. ClientNotify, when the response has been received from the server.
+   *
+   * Since we want to use these hooks to record the beginning and end of a COM
+   * IPC call, we use ClientGetSize for logging the start, and ClientNotify for
+   * logging the end.
+   *
+   * Finally, our implementation responds to any request matching our extension
+   * ID, however we only care about main thread COM calls.
+   */
+
+  // IChannelHook
+  STDMETHODIMP_(void)
+  ClientGetSize(REFGUID aExtensionId, REFIID aIid,
+                ULONG* aOutDataSize) override;
+
+  // No-op (see the large comment above)
+  STDMETHODIMP_(void)
+  ClientFillBuffer(REFGUID aExtensionId, REFIID aIid, ULONG* aDataSize,
+                   void* aDataBuf) override {}
+
+  STDMETHODIMP_(void)
+  ClientNotify(REFGUID aExtensionId, REFIID aIid, ULONG aDataSize,
+               void* aDataBuffer, DWORD aDataRep, HRESULT aFault) override;
+
+  // We don't care about the server-side notifications, so leave as no-ops.
+  STDMETHODIMP_(void)
+  ServerNotify(REFGUID aExtensionId, REFIID aIid, ULONG aDataSize,
+               void* aDataBuf, DWORD aDataRep) override {}
+
+  STDMETHODIMP_(void)
+  ServerGetSize(REFGUID aExtensionId, REFIID aIid, HRESULT aFault,
+                ULONG* aOutDataSize) override {}
+
+  STDMETHODIMP_(void)
+  ServerFillBuffer(REFGUID aExtensionId, REFIID aIid, ULONG* aDataSize,
+                   void* aDataBuf, HRESULT aFault) override {}
+
+ private:
+  void BuildMarkerName(REFIID aIid, nsACString& aOutMarkerName);
+
+ private:
+  mozilla::Atomic<ULONG> mRefCnt;
+};
+
+HRESULT ProfilerMarkerChannelHook::QueryInterface(REFIID aIid,
+                                                  void** aOutInterface) {
+  if (aIid == IID_IChannelHook || aIid == IID_IUnknown) {
+    RefPtr<IChannelHook> ptr(this);
+    ptr.forget(aOutInterface);
+    return S_OK;
+  }
+
+  return E_NOINTERFACE;
+}
+
+ULONG ProfilerMarkerChannelHook::AddRef() { return ++mRefCnt; }
+
+ULONG ProfilerMarkerChannelHook::Release() {
+  ULONG result = --mRefCnt;
+  if (!result) {
+    delete this;
+  }
+
+  return result;
+}
+
+void ProfilerMarkerChannelHook::BuildMarkerName(REFIID aIid,
+                                                nsACString& aOutMarkerName) {
+  aOutMarkerName.AssignLiteral("ORPC Call for ");
+
+  nsAutoCString iidStr;
+  mozilla::mscom::DiagnosticNameForIID(aIid, iidStr);
+  aOutMarkerName.Append(iidStr);
+}
+
+void ProfilerMarkerChannelHook::ClientGetSize(REFGUID aExtensionId, REFIID aIid,
+                                              ULONG* aOutDataSize) {
+  if (aExtensionId == GUID_MozProfilerMarkerExtension) {
+    if (NS_IsMainThread()) {
+      nsAutoCString markerName;
+      BuildMarkerName(aIid, markerName);
+      PROFILER_MARKER(markerName, IPC, mozilla::MarkerTiming::IntervalStart(),
+                      Tracing, "MSCOM");
+    }
+
+    if (aOutDataSize) {
+      // We don't add any payload data to the channel
+      *aOutDataSize = 0UL;
+    }
+  }
+}
+
+void ProfilerMarkerChannelHook::ClientNotify(REFGUID aExtensionId, REFIID aIid,
+                                             ULONG aDataSize, void* aDataBuffer,
+                                             DWORD aDataRep, HRESULT aFault) {
+  if (NS_IsMainThread() && aExtensionId == GUID_MozProfilerMarkerExtension) {
+    nsAutoCString markerName;
+    BuildMarkerName(aIid, markerName);
+    PROFILER_MARKER(markerName, IPC, mozilla::MarkerTiming::IntervalEnd(),
+                    Tracing, "MSCOM");
+  }
+}
+
+}  // anonymous namespace
+
+static void RegisterChannelHook() {
+  RefPtr<ProfilerMarkerChannelHook> hook(new ProfilerMarkerChannelHook());
+  mozilla::DebugOnly<HRESULT> hr =
+      ::CoRegisterChannelHook(GUID_MozProfilerMarkerExtension, hook);
+  MOZ_ASSERT(SUCCEEDED(hr));
+}
+
+namespace {
+
+class ProfilerStartupObserver final : public nsIObserver {
+  ~ProfilerStartupObserver() = default;
+
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIOBSERVER
+};
+
+NS_IMPL_ISUPPORTS(ProfilerStartupObserver, nsIObserver)
+
+NS_IMETHODIMP ProfilerStartupObserver::Observe(nsISupports* aSubject,
+                                               const char* aTopic,
+                                               const char16_t* aData) {
+  if (strcmp(aTopic, "profiler-started")) {
+    return NS_OK;
+  }
+
+  RegisterChannelHook();
+
+  // Once we've set the channel hook, we don't care about this notification
+  // anymore; our channel hook will remain set for the lifetime of the process.
+  nsCOMPtr<nsIObserverService> obsServ(mozilla::services::GetObserverService());
+  MOZ_ASSERT(!!obsServ);
+  if (!obsServ) {
+    return NS_OK;
+  }
+
+  obsServ->RemoveObserver(this, "profiler-started");
+  return NS_OK;
+}
+
+}  // anonymous namespace
+
+namespace mozilla {
+namespace mscom {
+
+void InitProfilerMarkers() {
+  if (!XRE_IsParentProcess()) {
+    return;
+  }
+
+  MOZ_ASSERT(NS_IsMainThread());
+  if (!NS_IsMainThread()) {
+    return;
+  }
+
+  if (profiler_is_active()) {
+    // If the profiler is already running, we'll immediately register our
+    // channel hook.
+    RegisterChannelHook();
+    return;
+  }
+
+  // The profiler is not running yet. To avoid unnecessary invocations of the
+  // channel hook, we won't bother with installing it until the profiler starts.
+  // Set up an observer to watch for this.
+  nsCOMPtr<nsIObserverService> obsServ(mozilla::services::GetObserverService());
+  MOZ_ASSERT(!!obsServ);
+  if (!obsServ) {
+    return;
+  }
+
+  nsCOMPtr<nsIObserver> obs(new ProfilerStartupObserver());
+  obsServ->AddObserver(obs, "profiler-started", false);
+}
+
+}  // namespace mscom
+}  // namespace mozilla
diff --git a/ipc/mscom/ProfilerMarkers.h b/ipc/mscom/ProfilerMarkers.h
new file mode 100644
index 0000000000..a21d5b375a
--- /dev/null
+++ b/ipc/mscom/ProfilerMarkers.h
@@ -0,0 +1,18 @@
+/* -*- 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_mscom_ProfilerMarkers_h
+#define mozilla_mscom_ProfilerMarkers_h
+
+namespace mozilla {
+namespace mscom {
+
+void InitProfilerMarkers();
+
+}  // namespace mscom
+}  // namespace mozilla
+
+#endif  // mozilla_mscom_ProfilerMarkers_h
diff --git a/ipc/mscom/Utils.cpp b/ipc/mscom/Utils.cpp
new file mode 100644
index 0000000000..a6aeebf12f
--- /dev/null
+++ b/ipc/mscom/Utils.cpp
@@ -0,0 +1,404 @@
+/* -*- 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/. */
+
+#if defined(MOZILLA_INTERNAL_API)
+#  include "MainThreadUtils.h"
+#  include "mozilla/dom/ContentChild.h"
+#endif
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/mscom/COMWrappers.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/mscom/Utils.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/WindowsVersion.h"
+
+#include <objidl.h>
+#include <shlwapi.h>
+#include <winnt.h>
+
+#include <utility>
+
+#if defined(_MSC_VER)
+extern "C" IMAGE_DOS_HEADER __ImageBase;
+#endif
+
+namespace mozilla {
+namespace mscom {
+
+bool IsCOMInitializedOnCurrentThread() {
+  APTTYPE aptType;
+  APTTYPEQUALIFIER aptTypeQualifier;
+  HRESULT hr = wrapped::CoGetApartmentType(&aptType, &aptTypeQualifier);
+  return hr != CO_E_NOTINITIALIZED;
+}
+
+bool IsCurrentThreadMTA() {
+  APTTYPE aptType;
+  APTTYPEQUALIFIER aptTypeQualifier;
+  HRESULT hr = wrapped::CoGetApartmentType(&aptType, &aptTypeQualifier);
+  if (FAILED(hr)) {
+    return false;
+  }
+
+  return aptType == APTTYPE_MTA;
+}
+
+bool IsCurrentThreadExplicitMTA() {
+  APTTYPE aptType;
+  APTTYPEQUALIFIER aptTypeQualifier;
+  HRESULT hr = wrapped::CoGetApartmentType(&aptType, &aptTypeQualifier);
+  if (FAILED(hr)) {
+    return false;
+  }
+
+  return aptType == APTTYPE_MTA &&
+         aptTypeQualifier != APTTYPEQUALIFIER_IMPLICIT_MTA;
+}
+
+bool IsCurrentThreadImplicitMTA() {
+  APTTYPE aptType;
+  APTTYPEQUALIFIER aptTypeQualifier;
+  HRESULT hr = wrapped::CoGetApartmentType(&aptType, &aptTypeQualifier);
+  if (FAILED(hr)) {
+    return false;
+  }
+
+  return aptType == APTTYPE_MTA &&
+         aptTypeQualifier == APTTYPEQUALIFIER_IMPLICIT_MTA;
+}
+
+#if defined(MOZILLA_INTERNAL_API)
+bool IsCurrentThreadNonMainMTA() {
+  if (NS_IsMainThread()) {
+    return false;
+  }
+
+  return IsCurrentThreadMTA();
+}
+#endif  // defined(MOZILLA_INTERNAL_API)
+
+bool IsProxy(IUnknown* aUnknown) {
+  if (!aUnknown) {
+    return false;
+  }
+
+  // Only proxies implement this interface, so if it is present then we must
+  // be dealing with a proxied object.
+  RefPtr<IClientSecurity> clientSecurity;
+  HRESULT hr = aUnknown->QueryInterface(IID_IClientSecurity,
+                                        (void**)getter_AddRefs(clientSecurity));
+  if (SUCCEEDED(hr) || hr == RPC_E_WRONG_THREAD) {
+    return true;
+  }
+  return false;
+}
+
+bool IsValidGUID(REFGUID aCheckGuid) {
+  // This function determines whether or not aCheckGuid conforms to RFC4122
+  // as it applies to Microsoft COM.
+
+  BYTE variant = aCheckGuid.Data4[0];
+  if (!(variant & 0x80)) {
+    // NCS Reserved
+    return false;
+  }
+  if ((variant & 0xE0) == 0xE0) {
+    // Reserved for future use
+    return false;
+  }
+  if ((variant & 0xC0) == 0xC0) {
+    // Microsoft Reserved.
+    return true;
+  }
+
+  BYTE version = HIBYTE(aCheckGuid.Data3) >> 4;
+  // Other versions are specified in RFC4122 but these are the two used by COM.
+  return version == 1 || version == 4;
+}
+
+uintptr_t GetContainingModuleHandle() {
+  HMODULE thisModule = nullptr;
+#if defined(_MSC_VER)
+  thisModule = reinterpret_cast<HMODULE>(&__ImageBase);
+#else
+  if (!GetModuleHandleEx(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS |
+                             GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT,
+                         reinterpret_cast<LPCTSTR>(&GetContainingModuleHandle),
+                         &thisModule)) {
+    return 0;
+  }
+#endif
+  return reinterpret_cast<uintptr_t>(thisModule);
+}
+
+namespace detail {
+
+long BuildRegGuidPath(REFGUID aGuid, const GuidType aGuidType, wchar_t* aBuf,
+                      const size_t aBufLen) {
+  constexpr wchar_t kClsid[] = L"CLSID\\";
+  constexpr wchar_t kAppid[] = L"AppID\\";
+  constexpr wchar_t kSubkeyBase[] = L"SOFTWARE\\Classes\\";
+
+  // We exclude null terminators in these length calculations because we include
+  // the stringified GUID's null terminator at the end. Since kClsid and kAppid
+  // have identical lengths, we just choose one to compute this length.
+  constexpr size_t kSubkeyBaseLen = mozilla::ArrayLength(kSubkeyBase) - 1;
+  constexpr size_t kSubkeyLen =
+      kSubkeyBaseLen + mozilla::ArrayLength(kClsid) - 1;
+  // Guid length as formatted for the registry (including curlies and dashes),
+  // but excluding null terminator.
+  constexpr size_t kGuidLen = kGuidRegFormatCharLenInclNul - 1;
+  constexpr size_t kExpectedPathLenInclNul = kSubkeyLen + kGuidLen + 1;
+
+  if (aBufLen < kExpectedPathLenInclNul) {
+    // Buffer is too short
+    return E_INVALIDARG;
+  }
+
+  if (wcscpy_s(aBuf, aBufLen, kSubkeyBase)) {
+    return E_INVALIDARG;
+  }
+
+  const wchar_t* strGuidType = aGuidType == GuidType::CLSID ? kClsid : kAppid;
+  if (wcscat_s(aBuf, aBufLen, strGuidType)) {
+    return E_INVALIDARG;
+  }
+
+  int guidConversionResult =
+      ::StringFromGUID2(aGuid, &aBuf[kSubkeyLen], aBufLen - kSubkeyLen);
+  if (!guidConversionResult) {
+    return E_INVALIDARG;
+  }
+
+  return S_OK;
+}
+
+}  // namespace detail
+
+long CreateStream(const uint8_t* aInitBuf, const uint32_t aInitBufSize,
+                  IStream** aOutStream) {
+  if (!aInitBufSize || !aOutStream) {
+    return E_INVALIDARG;
+  }
+
+  *aOutStream = nullptr;
+
+  HRESULT hr;
+  RefPtr<IStream> stream;
+
+  if (IsWin8OrLater()) {
+    // SHCreateMemStream is not safe for us to use until Windows 8. On older
+    // versions of Windows it is not thread-safe and it creates IStreams that do
+    // not support the full IStream API.
+
+    // If aInitBuf is null then initSize must be 0.
+    UINT initSize = aInitBuf ? aInitBufSize : 0;
+    stream = already_AddRefed<IStream>(::SHCreateMemStream(aInitBuf, initSize));
+    if (!stream) {
+      return E_OUTOFMEMORY;
+    }
+
+    if (!aInitBuf) {
+      // Now we'll set the required size
+      ULARGE_INTEGER newSize;
+      newSize.QuadPart = aInitBufSize;
+      hr = stream->SetSize(newSize);
+      if (FAILED(hr)) {
+        return hr;
+      }
+    }
+  } else {
+    HGLOBAL hglobal = ::GlobalAlloc(GMEM_MOVEABLE, aInitBufSize);
+    if (!hglobal) {
+      return HRESULT_FROM_WIN32(::GetLastError());
+    }
+
+    // stream takes ownership of hglobal if this call is successful
+    hr = ::CreateStreamOnHGlobal(hglobal, TRUE, getter_AddRefs(stream));
+    if (FAILED(hr)) {
+      ::GlobalFree(hglobal);
+      return hr;
+    }
+
+    // The default stream size is derived from ::GlobalSize(hglobal), which due
+    // to rounding may be larger than aInitBufSize. We forcibly set the correct
+    // stream size here.
+    ULARGE_INTEGER streamSize;
+    streamSize.QuadPart = aInitBufSize;
+    hr = stream->SetSize(streamSize);
+    if (FAILED(hr)) {
+      return hr;
+    }
+
+    if (aInitBuf) {
+      ULONG bytesWritten;
+      hr = stream->Write(aInitBuf, aInitBufSize, &bytesWritten);
+      if (FAILED(hr)) {
+        return hr;
+      }
+
+      if (bytesWritten != aInitBufSize) {
+        return E_UNEXPECTED;
+      }
+    }
+  }
+
+  // Ensure that the stream is rewound
+  LARGE_INTEGER streamOffset;
+  streamOffset.QuadPart = 0LL;
+  hr = stream->Seek(streamOffset, STREAM_SEEK_SET, nullptr);
+  if (FAILED(hr)) {
+    return hr;
+  }
+
+  stream.forget(aOutStream);
+  return S_OK;
+}
+
+#if defined(MOZILLA_INTERNAL_API)
+
+void GUIDToString(REFGUID aGuid, nsAString& aOutString) {
+  // This buffer length is long enough to hold a GUID string that is formatted
+  // to include curly braces and dashes.
+  const int kBufLenWithNul = 39;
+  aOutString.SetLength(kBufLenWithNul);
+  int result = StringFromGUID2(aGuid, char16ptr_t(aOutString.BeginWriting()),
+                               kBufLenWithNul);
+  MOZ_ASSERT(result);
+  if (result) {
+    // Truncate the terminator
+    aOutString.SetLength(result - 1);
+  }
+}
+
+// Undocumented IIDs that are relevant for diagnostic purposes
+static const IID IID_ISCMLocalActivator = {
+    0x00000136,
+    0x0000,
+    0x0000,
+    {0xC0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x46}};
+static const IID IID_IRundown = {
+    0x00000134,
+    0x0000,
+    0x0000,
+    {0xC0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x46}};
+static const IID IID_IRemUnknown = {
+    0x00000131,
+    0x0000,
+    0x0000,
+    {0xC0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x46}};
+static const IID IID_IRemUnknown2 = {
+    0x00000143,
+    0x0000,
+    0x0000,
+    {0xC0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x46}};
+
+struct IIDToLiteralMapEntry {
+  constexpr IIDToLiteralMapEntry(REFIID aIid, nsLiteralCString&& aStr)
+      : mIid(aIid), mStr(std::forward<nsLiteralCString>(aStr)) {}
+
+  REFIID mIid;
+  const nsLiteralCString mStr;
+};
+
+/**
+ * Given the name of an interface, the IID_ENTRY macro generates a pair
+ * containing a reference to the interface ID and a stringified version of
+ * the interface name.
+ *
+ * For example:
+ *
+ *   {IID_ENTRY(IUnknown)}
+ * is expanded to:
+ *   {IID_IUnknown, "IUnknown"_ns}
+ *
+ */
+// clang-format off
+#  define IID_ENTRY_STRINGIFY(iface) #iface##_ns
+#  define IID_ENTRY(iface) IID_##iface, IID_ENTRY_STRINGIFY(iface)
+// clang-format on
+
+// Mapping of selected IIDs to friendly, human readable descriptions for each
+// interface.
+static constexpr IIDToLiteralMapEntry sIidDiagStrs[] = {
+    {IID_ENTRY(IUnknown)},
+    {IID_IRemUnknown, "cross-apartment IUnknown"_ns},
+    {IID_IRundown, "cross-apartment object management"_ns},
+    {IID_ISCMLocalActivator, "out-of-process object instantiation"_ns},
+    {IID_IRemUnknown2, "cross-apartment IUnknown"_ns}};
+
+#  undef IID_ENTRY
+#  undef IID_ENTRY_STRINGIFY
+
+void DiagnosticNameForIID(REFIID aIid, nsACString& aOutString) {
+  // If the IID matches something in sIidDiagStrs, output its string.
+  for (const auto& curEntry : sIidDiagStrs) {
+    if (curEntry.mIid == aIid) {
+      aOutString.Assign(curEntry.mStr);
+      return;
+    }
+  }
+
+  // Otherwise just convert the IID to string form and output that.
+  nsAutoString strIid;
+  GUIDToString(aIid, strIid);
+
+  aOutString.AssignLiteral("IID ");
+  AppendUTF16toUTF8(strIid, aOutString);
+}
+
+#else
+
+void GUIDToString(REFGUID aGuid,
+                  wchar_t (&aOutBuf)[kGuidRegFormatCharLenInclNul]) {
+  DebugOnly<int> result =
+      ::StringFromGUID2(aGuid, aOutBuf, ArrayLength(aOutBuf));
+  MOZ_ASSERT(result);
+}
+
+#endif  // defined(MOZILLA_INTERNAL_API)
+
+#if defined(MOZILLA_INTERNAL_API)
+bool IsClassThreadAwareInprocServer(REFCLSID aClsid) {
+  nsAutoString strClsid;
+  GUIDToString(aClsid, strClsid);
+
+  nsAutoString inprocServerSubkey(u"CLSID\\"_ns);
+  inprocServerSubkey.Append(strClsid);
+  inprocServerSubkey.Append(u"\\InprocServer32"_ns);
+
+  // Of the possible values, "Apartment" is the longest, so we'll make this
+  // buffer large enough to hold that one.
+  wchar_t threadingModelBuf[ArrayLength(L"Apartment")] = {};
+
+  DWORD numBytes = sizeof(threadingModelBuf);
+  LONG result = ::RegGetValueW(HKEY_CLASSES_ROOT, inprocServerSubkey.get(),
+                               L"ThreadingModel", RRF_RT_REG_SZ, nullptr,
+                               threadingModelBuf, &numBytes);
+  if (result != ERROR_SUCCESS) {
+    // This will also handle the case where the CLSID is not an inproc server.
+    return false;
+  }
+
+  DWORD numChars = numBytes / sizeof(wchar_t);
+  // numChars includes the null terminator
+  if (numChars <= 1) {
+    return false;
+  }
+
+  nsDependentString threadingModel(threadingModelBuf, numChars - 1);
+
+  // Ensure that the threading model is one of the known values that indicates
+  // that the class can operate natively (ie, no proxying) inside a MTA.
+  return threadingModel.LowerCaseEqualsLiteral("both") ||
+         threadingModel.LowerCaseEqualsLiteral("free") ||
+         threadingModel.LowerCaseEqualsLiteral("neutral");
+}
+#endif  // defined(MOZILLA_INTERNAL_API)
+
+}  // namespace mscom
+}  // namespace mozilla
diff --git a/ipc/mscom/Utils.h b/ipc/mscom/Utils.h
new file mode 100644
index 0000000000..214b15044d
--- /dev/null
+++ b/ipc/mscom/Utils.h
@@ -0,0 +1,146 @@
+/* -*- 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_mscom_Utils_h
+#define mozilla_mscom_Utils_h
+
+#if defined(MOZILLA_INTERNAL_API)
+#  include "nsString.h"
+#endif  // defined(MOZILLA_INTERNAL_API)
+
+#include "mozilla/Attributes.h"
+#include <guiddef.h>
+#include <stdint.h>
+
+struct IStream;
+struct IUnknown;
+
+namespace mozilla {
+namespace mscom {
+namespace detail {
+
+enum class GuidType {
+  CLSID,
+  AppID,
+};
+
+long BuildRegGuidPath(REFGUID aGuid, const GuidType aGuidType, wchar_t* aBuf,
+                      const size_t aBufLen);
+
+}  // namespace detail
+
+bool IsCOMInitializedOnCurrentThread();
+bool IsCurrentThreadMTA();
+bool IsCurrentThreadExplicitMTA();
+bool IsCurrentThreadImplicitMTA();
+#if defined(MOZILLA_INTERNAL_API)
+bool IsCurrentThreadNonMainMTA();
+#endif  // defined(MOZILLA_INTERNAL_API)
+bool IsProxy(IUnknown* aUnknown);
+bool IsValidGUID(REFGUID aCheckGuid);
+uintptr_t GetContainingModuleHandle();
+
+template <size_t N>
+inline long BuildAppidPath(REFGUID aAppId, wchar_t (&aPath)[N]) {
+  return detail::BuildRegGuidPath(aAppId, detail::GuidType::AppID, aPath, N);
+}
+
+template <size_t N>
+inline long BuildClsidPath(REFCLSID aClsid, wchar_t (&aPath)[N]) {
+  return detail::BuildRegGuidPath(aClsid, detail::GuidType::CLSID, aPath, N);
+}
+
+/**
+ * Given a buffer, create a new IStream object.
+ * @param aBuf Buffer containing data to initialize the stream. This parameter
+ *             may be nullptr, causing the stream to be created with aBufLen
+ *             bytes of uninitialized data.
+ * @param aBufLen Length of data in aBuf, or desired stream size if aBuf is
+ *                nullptr.
+ * @param aOutStream Outparam to receive the newly created stream.
+ * @return HRESULT error code.
+ */
+long CreateStream(const uint8_t* aBuf, const uint32_t aBufLen,
+                  IStream** aOutStream);
+
+/**
+ * Length of a stringified GUID as formatted for the registry, i.e. including
+ * curly-braces and dashes.
+ */
+constexpr size_t kGuidRegFormatCharLenInclNul = 39;
+
+#if defined(MOZILLA_INTERNAL_API)
+/**
+ * Checks the registry to see if |aClsid| is a thread-aware in-process server.
+ *
+ * In DCOM, an in-process server is a server that is implemented inside a DLL
+ * that is loaded into the client's process for execution. If |aClsid| declares
+ * itself to be a local server (that is, a server that resides in another
+ * process), this function returns false.
+ *
+ * For the server to be thread-aware, its registry entry must declare a
+ * ThreadingModel that is one of "Free", "Both", or "Neutral". If the threading
+ * model is "Apartment" or some other, invalid value, the class is treated as
+ * being single-threaded.
+ *
+ * NB: This function cannot check CLSIDs that were registered via manifests,
+ * as unfortunately there is not a documented API available to query for those.
+ * This should not be an issue for most CLSIDs that Gecko is interested in, as
+ * we typically instantiate system CLSIDs which are available in the registry.
+ *
+ * @param aClsid The CLSID of the COM class to be checked.
+ * @return true if the class meets the above criteria, otherwise false.
+ */
+bool IsClassThreadAwareInprocServer(REFCLSID aClsid);
+
+void GUIDToString(REFGUID aGuid, nsAString& aOutString);
+
+/**
+ * Converts an IID to a human-readable string for the purposes of diagnostic
+ * tools such as the profiler. For some special cases, we output a friendly
+ * string that describes the purpose of the interface. If no such description
+ * exists, we simply fall back to outputting the IID as a string formatted by
+ * GUIDToString().
+ */
+void DiagnosticNameForIID(REFIID aIid, nsACString& aOutString);
+#else
+void GUIDToString(REFGUID aGuid,
+                  wchar_t (&aOutBuf)[kGuidRegFormatCharLenInclNul]);
+#endif  // defined(MOZILLA_INTERNAL_API)
+
+/**
+ * Execute cleanup code when going out of scope if a condition is met.
+ * This is useful when, for example, particular cleanup needs to be performed
+ * whenever a call returns a failure HRESULT.
+ * Both the condition and cleanup code are provided as functions (usually
+ * lambdas).
+ */
+template <typename CondFnT, typename ExeFnT>
+class MOZ_RAII ExecuteWhen final {
+ public:
+  ExecuteWhen(CondFnT& aCondFn, ExeFnT& aExeFn)
+      : mCondFn(aCondFn), mExeFn(aExeFn) {}
+
+  ~ExecuteWhen() {
+    if (mCondFn()) {
+      mExeFn();
+    }
+  }
+
+  ExecuteWhen(const ExecuteWhen&) = delete;
+  ExecuteWhen(ExecuteWhen&&) = delete;
+  ExecuteWhen& operator=(const ExecuteWhen&) = delete;
+  ExecuteWhen& operator=(ExecuteWhen&&) = delete;
+
+ private:
+  CondFnT& mCondFn;
+  ExeFnT& mExeFn;
+};
+
+}  // namespace mscom
+}  // namespace mozilla
+
+#endif  // mozilla_mscom_Utils_h
diff --git a/ipc/mscom/moz.build b/ipc/mscom/moz.build
new file mode 100644
index 0000000000..e11b7314f4
--- /dev/null
+++ b/ipc/mscom/moz.build
@@ -0,0 +1,42 @@
+# -*- 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/.
+
+EXPORTS.mozilla.mscom += [
+    "Aggregation.h",
+    "AgileReference.h",
+    "ApartmentRegion.h",
+    "COMWrappers.h",
+    "EnsureMTA.h",
+    "ProcessRuntime.h",
+    "ProfilerMarkers.h",
+    "Utils.h",
+]
+
+DIRS += [
+    "mozglue",
+]
+
+UNIFIED_SOURCES += [
+    "AgileReference.cpp",
+    "COMWrappers.cpp",
+    "EnsureMTA.cpp",
+    "ProcessRuntime.cpp",
+    "ProfilerMarkers.cpp",
+    "Utils.cpp",
+]
+
+LOCAL_INCLUDES += [
+    "/xpcom/base",
+    "/xpcom/build",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"
+
+with Files("**"):
+    BUG_COMPONENT = ("Core", "IPC: MSCOM")
+    SCHEDULES.exclusive = ["windows"]
diff --git a/ipc/mscom/mozglue/ProcessRuntimeShared.cpp b/ipc/mscom/mozglue/ProcessRuntimeShared.cpp
new file mode 100644
index 0000000000..ee4f6b221f
--- /dev/null
+++ b/ipc/mscom/mozglue/ProcessRuntimeShared.cpp
@@ -0,0 +1,31 @@
+/* -*- 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/mscom/ProcessRuntimeShared.h"
+
+#include "mozilla/glue/WinUtils.h"
+
+// We allow multiple ProcessRuntime instances to exist simultaneously (even
+// on separate threads), but only one should be doing the process-wide
+// initialization. These variables provide that mutual exclusion.
+static mozilla::glue::Win32SRWLock gLock;
+static mozilla::mscom::detail::ProcessInitState gProcessInitState =
+    mozilla::mscom::detail::ProcessInitState::Uninitialized;
+
+namespace mozilla {
+namespace mscom {
+namespace detail {
+
+MFBT_API ProcessInitState& BeginProcessRuntimeInit() {
+  gLock.LockExclusive();
+  return gProcessInitState;
+}
+
+MFBT_API void EndProcessRuntimeInit() { gLock.UnlockExclusive(); }
+
+}  // namespace detail
+}  // namespace mscom
+}  // namespace mozilla
diff --git a/ipc/mscom/mozglue/ProcessRuntimeShared.h b/ipc/mscom/mozglue/ProcessRuntimeShared.h
new file mode 100644
index 0000000000..d5a58a7b92
--- /dev/null
+++ b/ipc/mscom/mozglue/ProcessRuntimeShared.h
@@ -0,0 +1,55 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_mscom_ProcessRuntimeShared_h
+#define mozilla_mscom_ProcessRuntimeShared_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/Types.h"
+
+namespace mozilla {
+namespace mscom {
+namespace detail {
+
+enum class ProcessInitState : uint32_t {
+  Uninitialized = 0,
+  PartialSecurityInitialized,
+  PartialGlobalOptions,
+  FullyInitialized,
+};
+
+MFBT_API ProcessInitState& BeginProcessRuntimeInit();
+MFBT_API void EndProcessRuntimeInit();
+
+}  // namespace detail
+
+class MOZ_RAII ProcessInitLock final {
+ public:
+  ProcessInitLock() : mInitState(detail::BeginProcessRuntimeInit()) {}
+
+  ~ProcessInitLock() { detail::EndProcessRuntimeInit(); }
+
+  detail::ProcessInitState GetInitState() const { return mInitState; }
+
+  void SetInitState(const detail::ProcessInitState aNewState) {
+    MOZ_DIAGNOSTIC_ASSERT(aNewState > mInitState);
+    mInitState = aNewState;
+  }
+
+  ProcessInitLock(const ProcessInitLock&) = delete;
+  ProcessInitLock(ProcessInitLock&&) = delete;
+  ProcessInitLock operator=(const ProcessInitLock&) = delete;
+  ProcessInitLock operator=(ProcessInitLock&&) = delete;
+
+ private:
+  detail::ProcessInitState& mInitState;
+};
+
+}  // namespace mscom
+}  // namespace mozilla
+
+#endif  // mozilla_mscom_ProcessRuntimeShared_h
diff --git a/ipc/mscom/mozglue/moz.build b/ipc/mscom/mozglue/moz.build
new file mode 100644
index 0000000000..f52a772324
--- /dev/null
+++ b/ipc/mscom/mozglue/moz.build
@@ -0,0 +1,15 @@
+# -*- 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/.
+
+FINAL_LIBRARY = "mozglue"
+
+EXPORTS.mozilla.mscom += [
+    "ProcessRuntimeShared.h",
+]
+
+UNIFIED_SOURCES += [
+    "ProcessRuntimeShared.cpp",
+]