Create manager to track OffscreenCanvasSurfaceImpl instances

content/browser/renderer_host/offscreen_canvas_compositor_frame_sink.h

Index: content/browser/renderer_host/offscreen_canvas_compositor_frame_sink.h
diff --git a/content/browser/renderer_host/offscreen_canvas_compositor_frame_sink.h b/content/browser/renderer_host/offscreen_canvas_compositor_frame_sink.h
index 0d838ed11ee7831824cd70a4c261ecee3962336f..6da8c80ea67079230a8af76a821b52ad0f0e86c6 100644
--- a/content/browser/renderer_host/offscreen_canvas_compositor_frame_sink.h
+++ b/content/browser/renderer_host/offscreen_canvas_compositor_frame_sink.h
@@ -11,7 +11,7 @@
 
 namespace content {
 
-class OffscreenCanvasCompositorFrameSink
+class CONTENT_EXPORT OffscreenCanvasCompositorFrameSink
     : public cc::mojom::MojoCompositorFrameSink,
       public cc::SurfaceFactoryClient {
  public:
@@ -34,6 +34,14 @@ class OffscreenCanvasCompositorFrameSink
                        const gfx::Rect& damage_rect) override;
   void SetBeginFrameSource(cc::BeginFrameSource* begin_frame_source) override;
 
+  const cc::FrameSinkId& frame_sink_id() const {
+    return surface_id_.frame_sink_id();
+  }
+
+  base::WeakPtr<OffscreenCanvasCompositorFrameSink> GetWeakPtr() {
+    return weak_factory_.GetWeakPtr();
+  }
+
  private:
   void DidReceiveCompositorFrameAck();
 
@@ -43,6 +51,8 @@ class OffscreenCanvasCompositorFrameSink
   int ack_pending_count_ = 0;
   cc::ReturnedResourceArray surface_returned_resources_;
 
+  base::WeakPtrFactory<OffscreenCanvasCompositorFrameSink> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(OffscreenCanvasCompositorFrameSink);
 };