Add observers to FrameSinkManagerHost.

content/browser/renderer_host/offscreen_canvas_provider_impl.h

Index: content/browser/renderer_host/offscreen_canvas_provider_impl.h
diff --git a/content/browser/renderer_host/offscreen_canvas_provider_impl.h b/content/browser/renderer_host/offscreen_canvas_provider_impl.h
index 554e121a39a7b453d9d4a82aaf9ee8a8e05f1ea8..75ae94fe58ee402db6eccb614cd13e138c17d480 100644
--- a/content/browser/renderer_host/offscreen_canvas_provider_impl.h
+++ b/content/browser/renderer_host/offscreen_canvas_provider_impl.h
@@ -5,14 +5,20 @@
 #ifndef CONTENT_BROWSER_RENDERER_HOST_OFFSCREEN_CANVAS_PROVIDER_IMPL_H_
 #define CONTENT_BROWSER_RENDERER_HOST_OFFSCREEN_CANVAS_PROVIDER_IMPL_H_
 
+#include <memory>
+#include <unordered_map>
+
 #include "cc/surfaces/frame_sink_id.h"
+#include "content/common/content_export.h"
 #include "mojo/public/cpp/bindings/binding_set.h"
 #include "third_party/WebKit/public/platform/modules/offscreencanvas/offscreen_canvas_surface.mojom.h"
 
 namespace content {
 
+class OffscreenCanvasSurfaceImpl;
+
 // Creates OffscreenCanvasSurfaces and MojoCompositorFrameSinks for a renderer.
-class OffscreenCanvasProviderImpl
+class CONTENT_EXPORT OffscreenCanvasProviderImpl
     : public blink::mojom::OffscreenCanvasProvider {
  public:
   explicit OffscreenCanvasProviderImpl(uint32_t renderer_client_id);
@@ -20,6 +26,8 @@ class OffscreenCanvasProviderImpl
 
   void Add(blink::mojom::OffscreenCanvasProviderRequest request);
 
+  void DestroyOffscreenCanvasSurface(const cc::FrameSinkId& frame_sink_id);

[Fady Samuel, 2017/04/28 04:58:00]

Should this be passed by value to avoid use-after-free?

[kylechar, 2017/05/01 19:07:48]

Done.

+
   // blink::mojom::OffscreenCanvasProvider implementation.
   void CreateOffscreenCanvasSurface(
       const cc::FrameSinkId& parent_frame_sink_id,
@@ -32,11 +40,18 @@ class OffscreenCanvasProviderImpl
       cc::mojom::MojoCompositorFrameSinkRequest request) override;
 
  private:
+  friend class OffscreenCanvasProviderImplTest;
+
   // FrameSinkIds for offscreen canvas must use the renderer client id.
   const uint32_t renderer_client_id_;
 
   mojo::BindingSet<blink::mojom::OffscreenCanvasProvider> bindings_;
 
+  std::unordered_map<cc::FrameSinkId,
+                     std::unique_ptr<OffscreenCanvasSurfaceImpl>,
+                     cc::FrameSinkIdHash>
+      surfaces_;

[Fady Samuel, 2017/04/28 04:58:00]

I hate how we're overloading the term surface here :(

[kylechar, 2017/05/01 19:07:48]

Agreed. I think it should be OffscreenCanvasSurfaceImpl => OffscreenCanvasImpl.

+
   DISALLOW_COPY_AND_ASSIGN(OffscreenCanvasProviderImpl);
 };