Bug 1551735 - Ref count and document CompositionRecorder r=kats

The CompositionRecorder was being stored as a UniquePtr on the
CompositorBridgeParent, but was then passed to and stored on the LayerManger as
a raw pointer. This has been updated to use a RefPtr.

Differential Revision: https://phabricator.services.mozilla.com/D32230

--HG--
extra : moz-landing-system : lando

gfx/layers/CompositionRecorder.h

@@ -20,6 +20,9 @@ class DataSourceSurface;
 
 namespace layers {
 
+/**
+ * A captured frame from a |LayerManager|.
+ */
 class RecordedFrame {
  public:
   NS_INLINE_DECL_THREADSAFE_REFCOUNTING(RecordedFrame)
@@ -38,17 +41,33 @@ class RecordedFrame {
 };
 
 /**
+ * A recorder for composited frames.
  *
+ * This object collects frames sent to it by a |LayerManager| and writes them
+ * out as a series of images until recording has finished.
+ *
+ * If GPU-accelerated rendering is used, the frames will not be mapped into
+ * memory until |WriteCollectedFrames| is called.
  */
 class CompositionRecorder final {
+  NS_INLINE_DECL_REFCOUNTING(CompositionRecorder)
+
  public:
   explicit CompositionRecorder(TimeStamp aRecordingStart);
-  ~CompositionRecorder();
 
+  /**
+   * Record a composited frame.
+   */
   void RecordFrame(RecordedFrame* aFrame);
 
+  /**
+   * Write out the collected frames as a series of timestamped images.
+   */
   void WriteCollectedFrames();
 
+ protected:
+  ~CompositionRecorder();
+
  private:
   nsTArray<RefPtr<RecordedFrame>> mCollectedFrames;
   TimeStamp mRecordingStart;
@@ -57,4 +76,4 @@ class CompositionRecorder final {
 }  // namespace layers
 }  // namespace mozilla
 
-#endif  // mozilla_layers_ProfilerScreenshots_h
+#endif  // mozilla_layers_CompositionRecorder_h

gfx/layers/composite/LayerManagerComposite.h

@@ -19,6 +19,7 @@
 #include "mozilla/gfx/Point.h"  // for IntSize
 #include "mozilla/gfx/Rect.h"   // for Rect
 #include "mozilla/gfx/Types.h"  // for SurfaceFormat
+#include "mozilla/layers/CompositionRecorder.h"
 #include "mozilla/layers/CompositorTypes.h"
 #include "mozilla/layers/Effects.h"  // for EffectChain
 #include "mozilla/layers/LayersMessages.h"
@@ -53,7 +54,6 @@ namespace layers {
 class CanvasLayerComposite;
 class ColorLayerComposite;
 class Compositor;
-class CompositionRecorder;
 class ContainerLayerComposite;
 class Diagnostics;
 struct EffectChain;
@@ -199,7 +199,7 @@ class HostLayerManager : public LayerManager {
     mCompositorBridgeID = aID;
   }
 
-  void SetCompositionRecorder(CompositionRecorder* aRecorder) {
+  void SetCompositionRecorder(already_AddRefed<CompositionRecorder> aRecorder) {
     mCompositionRecorder = aRecorder;
   }
 
@@ -216,7 +216,7 @@ class HostLayerManager : public LayerManager {
   bool mWindowOverlayChanged;
   TimeDuration mLastPaintTime;
   TimeStamp mRenderStartTime;
-  CompositionRecorder* mCompositionRecorder = nullptr;
+  RefPtr<CompositionRecorder> mCompositionRecorder = nullptr;
 
   // Render time for the current composition.
   TimeStamp mCompositionTime;

gfx/layers/ipc/CompositorBridgeParent.cpp

@@ -2609,10 +2609,10 @@ int32_t RecordContentFrameTime(
 
 mozilla::ipc::IPCResult CompositorBridgeParent::RecvBeginRecording(
     const TimeStamp& aRecordingStart) {
-  mCompositionRecorder.reset(new CompositionRecorder(aRecordingStart));
+  mCompositionRecorder = new CompositionRecorder(aRecordingStart);
 
   if (mLayerManager) {
-    mLayerManager->SetCompositionRecorder(mCompositionRecorder.get());
+    mLayerManager->SetCompositionRecorder(do_AddRef(mCompositionRecorder));
   }
 
   return IPC_OK();
@@ -2623,7 +2623,7 @@ mozilla::ipc::IPCResult CompositorBridgeParent::RecvEndRecording() {
     mLayerManager->SetCompositionRecorder(nullptr);
   }
   mCompositionRecorder->WriteCollectedFrames();
-  mCompositionRecorder.reset(nullptr);
+  mCompositionRecorder = nullptr;
   return IPC_OK();
 }
 

gfx/layers/ipc/CompositorBridgeParent.h

@@ -27,6 +27,7 @@
 #include "mozilla/gfx/Point.h"  // for IntSize
 #include "mozilla/ipc/ProtocolUtils.h"
 #include "mozilla/ipc/SharedMemory.h"
+#include "mozilla/layers/CompositionRecorder.h"
 #include "mozilla/layers/CompositorController.h"
 #include "mozilla/layers/CompositorOptions.h"
 #include "mozilla/layers/CompositorVsyncSchedulerOwner.h"
@@ -72,7 +73,6 @@ class APZSampler;
 class APZUpdater;
 class AsyncCompositionManager;
 class AsyncImagePipelineManager;
-class CompositionRecorder;
 class Compositor;
 class CompositorAnimationStorage;
 class CompositorBridgeParent;
@@ -767,7 +767,7 @@ class CompositorBridgeParent final : public CompositorBridgeParentBase,
   // mSelfRef is cleared in DeferredDestroy which is scheduled by ActorDestroy.
   RefPtr<CompositorBridgeParent> mSelfRef;
   RefPtr<CompositorAnimationStorage> mAnimationStorage;
-  UniquePtr<CompositionRecorder> mCompositionRecorder;
+  RefPtr<CompositionRecorder> mCompositionRecorder;
 
   TimeDuration mPaintTime;