Revamp OffscreenCanvas commit flow

third_party/WebKit/Source/platform/graphics/CanvasSurfaceLayerBridge.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CanvasSurfaceLayerBridge_h
 #define CanvasSurfaceLayerBridge_h
 
 #include "base/memory/ref_counted.h"
 #include "cc/surfaces/surface_id.h"
+#include "mojo/public/cpp/bindings/binding.h"
 #include "platform/PlatformExport.h"
 #include "public/platform/modules/offscreencanvas/offscreen_canvas_surface.mojom-blink.h"
 #include <memory>
 
 namespace cc {
+class SolidColorLayer;
 class SurfaceLayer;
 struct SurfaceSequence;
 }  // namespace cc
 
 namespace blink {
 
 class WebLayer;
 
-class PLATFORM_EXPORT CanvasSurfaceLayerBridge {
+class PLATFORM_EXPORT CanvasSurfaceLayerBridgeObserver {
  public:
-  explicit CanvasSurfaceLayerBridge(mojom::blink::OffscreenCanvasSurfacePtr);
+  CanvasSurfaceLayerBridgeObserver() {}
+  virtual ~CanvasSurfaceLayerBridgeObserver() {}
+
+  virtual void OnWebLayerReplaced() = 0;
+};
+
+class PLATFORM_EXPORT CanvasSurfaceLayerBridge
+    : NON_EXPORTED_BASE(public mojom::blink::OffscreenCanvasSurfaceClient) {
+ public:
+  explicit CanvasSurfaceLayerBridge(mojom::blink::OffscreenCanvasSurfacePtr,
+                                    CanvasSurfaceLayerBridgeObserver*);
   ~CanvasSurfaceLayerBridge();
-  bool createSurfaceLayer(int canvasWidth, int canvasHeight);
+  void createSolidColorLayer();
   WebLayer* getWebLayer() const { return m_webLayer.get(); }
-  const cc::SurfaceId& getSurfaceId() const { return m_surfaceId; }
+  const cc::FrameSinkId& getFrameSinkId() const { return m_frameSinkId; }
+
+  // Implementation of mojom::blink::OffscreenCanvasSurfaceClient
+  void OnSurfaceCreated(const cc::SurfaceId&,
+                        int32_t width,
+                        int32_t height,
+                        float deviceScaleFactor) override;
 
   void satisfyCallback(const cc::SurfaceSequence&);
   void requireCallback(const cc::SurfaceId&, const cc::SurfaceSequence&);
 
  private:
   scoped_refptr<cc::SurfaceLayer> m_surfaceLayer;
+  scoped_refptr<cc::SolidColorLayer> m_solidColorLayer;

[Justin Novosad, 2016/12/15 22:19:35]

It would be cleaner to have a single reference to a layer.  This should work:
scoped_refptr<cc::Layer> m_layer;  
Unless there is a reason for both layers to exist at the same time.
BTW, I noticed that in OnSurfaceCreated you are not discarding m_solidColorLayer
is that on purpose?

[xlai (Olivia), 2016/12/15 22:46:27]

Done. I shouldn't keep the SolidColorLayer; that was a mistake. With only one
cc::Layer ref ptr now, this issue should be resolved.

   std::unique_ptr<WebLayer> m_webLayer;
+
+  CanvasSurfaceLayerBridgeObserver* m_observer;
+
   mojom::blink::OffscreenCanvasSurfacePtr m_service;
-  cc::SurfaceId m_surfaceId;
+  mojo::Binding<mojom::blink::OffscreenCanvasSurfaceClient> m_binding;
+
+  cc::FrameSinkId m_frameSinkId;
+  cc::SurfaceId m_currentSurfaceId;
 };
 
 }  // namespace blink
 
 #endif  // CanvasSurfaceLayerBridge_h