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diff --git a/gfx/layers/ipc/KnowsCompositor.h b/gfx/layers/ipc/KnowsCompositor.h
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+++ b/gfx/layers/ipc/KnowsCompositor.h
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+/* -*- 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_LAYERS_KNOWSCOMPOSITOR
+#define MOZILLA_LAYERS_KNOWSCOMPOSITOR
+
+#include "mozilla/layers/LayersTypes.h"  // for LayersBackend
+#include "mozilla/layers/CompositorTypes.h"
+#include "nsExpirationTracker.h"
+#include "mozilla/DataMutex.h"
+#include "mozilla/layers/SyncObject.h"
+
+namespace mozilla {
+namespace layers {
+
+class TextureForwarder;
+class LayersIPCActor;
+class ImageBridgeChild;
+
+/**
+ * See ActiveResourceTracker below.
+ */
+class ActiveResource {
+ public:
+  virtual void NotifyInactive() = 0;
+  nsExpirationState* GetExpirationState() { return &mExpirationState; }
+  bool IsActivityTracked() { return mExpirationState.IsTracked(); }
+
+ private:
+  nsExpirationState mExpirationState;
+};
+
+/**
+ * A convenience class on top of nsExpirationTracker
+ */
+class ActiveResourceTracker : public nsExpirationTracker<ActiveResource, 3> {
+ public:
+  ActiveResourceTracker(uint32_t aExpirationCycle, const char* aName,
+                        nsIEventTarget* aEventTarget)
+      : nsExpirationTracker(aExpirationCycle, aName, aEventTarget) {}
+
+  void NotifyExpired(ActiveResource* aResource) override {
+    RemoveObject(aResource);
+    aResource->NotifyInactive();
+  }
+};
+
+/**
+ * An abstract interface for classes that are tied to a specific Compositor
+ * across IPDL and uses TextureFactoryIdentifier to describe this Compositor.
+ */
+class KnowsCompositor {
+ public:
+  NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
+
+  KnowsCompositor();
+  virtual ~KnowsCompositor();
+
+  void IdentifyTextureHost(const TextureFactoryIdentifier& aIdentifier);
+
+  // The sync object for the global content device.
+  RefPtr<SyncObjectClient> GetSyncObject() {
+    auto lock = mData.Lock();
+    if (lock.ref().mSyncObject) {
+      lock.ref().mSyncObject->EnsureInitialized();
+    }
+    return lock.ref().mSyncObject;
+  }
+
+  /// And by "thread-safe" here we merely mean "okay to hold strong references
+  /// to from multiple threads". Not all methods actually are thread-safe.
+  virtual bool IsThreadSafe() const { return true; }
+
+  virtual RefPtr<KnowsCompositor> GetForMedia() {
+    return RefPtr<KnowsCompositor>(this);
+  }
+
+  int32_t GetMaxTextureSize() const {
+    auto lock = mData.Lock();
+    return lock.ref().mTextureFactoryIdentifier.mMaxTextureSize;
+  }
+
+  /**
+   * Returns the type of backend that is used off the main thread.
+   * We only don't allow changing the backend type at runtime so this value can
+   * be queried once and will not change until Gecko is restarted.
+   */
+  LayersBackend GetCompositorBackendType() const {
+    auto lock = mData.Lock();
+    return lock.ref().mTextureFactoryIdentifier.mParentBackend;
+  }
+
+  WebRenderCompositor GetWebRenderCompositorType() const {
+    auto lock = mData.Lock();
+    return lock.ref().mTextureFactoryIdentifier.mWebRenderCompositor;
+  }
+
+  bool SupportsTextureBlitting() const {
+    auto lock = mData.Lock();
+    return lock.ref().mTextureFactoryIdentifier.mSupportsTextureBlitting;
+  }
+
+  bool SupportsPartialUploads() const {
+    auto lock = mData.Lock();
+    return lock.ref().mTextureFactoryIdentifier.mSupportsPartialUploads;
+  }
+
+  bool SupportsComponentAlpha() const {
+    auto lock = mData.Lock();
+    return lock.ref().mTextureFactoryIdentifier.mSupportsComponentAlpha;
+  }
+
+  bool SupportsD3D11NV12() const {
+    auto lock = mData.Lock();
+    return lock.ref().mTextureFactoryIdentifier.mSupportsD3D11NV12;
+  }
+
+  bool SupportsD3D11() const {
+    auto lock = mData.Lock();
+    return lock.ref().mTextureFactoryIdentifier.mParentBackend ==
+               layers::LayersBackend::LAYERS_WR &&
+           (lock.ref().mTextureFactoryIdentifier.mCompositorUseANGLE ||
+            lock.ref().mTextureFactoryIdentifier.mWebRenderCompositor ==
+                layers::WebRenderCompositor::D3D11);
+  }
+
+  bool GetCompositorUseANGLE() const {
+    auto lock = mData.Lock();
+    return lock.ref().mTextureFactoryIdentifier.mCompositorUseANGLE;
+  }
+
+  bool GetCompositorUseDComp() const {
+    auto lock = mData.Lock();
+    return lock.ref().mTextureFactoryIdentifier.mCompositorUseDComp;
+  }
+
+  bool GetUseCompositorWnd() const {
+    auto lock = mData.Lock();
+    return lock.ref().mTextureFactoryIdentifier.mUseCompositorWnd;
+  }
+
+  WebRenderBackend GetWebRenderBackend() const {
+    auto lock = mData.Lock();
+    MOZ_ASSERT(lock.ref().mTextureFactoryIdentifier.mParentBackend ==
+               layers::LayersBackend::LAYERS_WR);
+    return lock.ref().mTextureFactoryIdentifier.mWebRenderBackend;
+  }
+
+  bool UsingHardwareWebRender() const {
+    auto lock = mData.Lock();
+    return lock.ref().mTextureFactoryIdentifier.mParentBackend ==
+               layers::LayersBackend::LAYERS_WR &&
+           lock.ref().mTextureFactoryIdentifier.mWebRenderBackend ==
+               WebRenderBackend::HARDWARE;
+  }
+
+  bool UsingSoftwareWebRender() const {
+    auto lock = mData.Lock();
+    return lock.ref().mTextureFactoryIdentifier.mParentBackend ==
+               layers::LayersBackend::LAYERS_WR &&
+           lock.ref().mTextureFactoryIdentifier.mWebRenderBackend ==
+               WebRenderBackend::SOFTWARE;
+  }
+
+  bool UsingSoftwareWebRenderD3D11() const {
+    auto lock = mData.Lock();
+    return lock.ref().mTextureFactoryIdentifier.mParentBackend ==
+               layers::LayersBackend::LAYERS_WR &&
+           lock.ref().mTextureFactoryIdentifier.mWebRenderBackend ==
+               WebRenderBackend::SOFTWARE &&
+           lock.ref().mTextureFactoryIdentifier.mWebRenderCompositor ==
+               layers::WebRenderCompositor::D3D11;
+  }
+
+  bool UsingSoftwareWebRenderOpenGL() const {
+    auto lock = mData.Lock();
+    return lock.ref().mTextureFactoryIdentifier.mParentBackend ==
+               layers::LayersBackend::LAYERS_WR &&
+           lock.ref().mTextureFactoryIdentifier.mWebRenderBackend ==
+               WebRenderBackend::SOFTWARE &&
+           lock.ref().mTextureFactoryIdentifier.mWebRenderCompositor ==
+               layers::WebRenderCompositor::OPENGL;
+  }
+
+  TextureFactoryIdentifier GetTextureFactoryIdentifier() const {
+    auto lock = mData.Lock();
+    return lock.ref().mTextureFactoryIdentifier;
+  }
+
+  int32_t GetSerial() const { return mSerial; }
+
+  /**
+   * Sends a synchronous ping to the compsoitor.
+   *
+   * This is bad for performance and should only be called as a last resort if
+   * the compositor may be blocked for a long period of time, to avoid that the
+   * content process accumulates resource allocations that the compositor is not
+   * consuming and releasing.
+   */
+  virtual void SyncWithCompositor() { MOZ_ASSERT_UNREACHABLE("Unimplemented"); }
+
+  /**
+   * Helpers for finding other related interface. These are infallible.
+   */
+  virtual TextureForwarder* GetTextureForwarder() = 0;
+  virtual LayersIPCActor* GetLayersIPCActor() = 0;
+  virtual ActiveResourceTracker* GetActiveResourceTracker() {
+    MOZ_ASSERT_UNREACHABLE("Unimplemented");
+    return nullptr;
+  }
+
+ protected:
+  struct SharedData {
+    TextureFactoryIdentifier mTextureFactoryIdentifier;
+    RefPtr<SyncObjectClient> mSyncObject;
+  };
+  mutable DataMutex<SharedData> mData;
+
+  const int32_t mSerial;
+  static mozilla::Atomic<int32_t> sSerialCounter;
+};
+
+/// Some implementations of KnowsCompositor can be used off their IPDL thread
+/// like the ImageBridgeChild, and others just can't. Instead of passing them
+/// we create a proxy KnowsCompositor that has information about compositor
+/// backend but proxies allocations to the ImageBridge.
+/// This is kind of specific to the needs of media which wants to allocate
+/// textures, usually through the Image Bridge accessed by KnowsCompositor but
+/// also wants access to the compositor backend information that ImageBridge
+/// doesn't know about.
+///
+/// This is really a band aid to what turned into a class hierarchy horror show.
+/// Hopefully we can come back and simplify this some way.
+class KnowsCompositorMediaProxy : public KnowsCompositor {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(KnowsCompositorMediaProxy, override);
+
+  explicit KnowsCompositorMediaProxy(
+      const TextureFactoryIdentifier& aIdentifier);
+
+  TextureForwarder* GetTextureForwarder() override;
+
+  LayersIPCActor* GetLayersIPCActor() override;
+
+  ActiveResourceTracker* GetActiveResourceTracker() override;
+
+  void SyncWithCompositor() override;
+
+ protected:
+  virtual ~KnowsCompositorMediaProxy();
+
+  RefPtr<ImageBridgeChild> mThreadSafeAllocator;
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif