WIP: Surface Synchronization System

cc/layers/surface_layer.h

 // Copyright 2014 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 CC_LAYERS_SURFACE_LAYER_H_
 #define CC_LAYERS_SURFACE_LAYER_H_
 
 #include "base/macros.h"
 #include "cc/base/cc_export.h"
 #include "cc/layers/layer.h"
 #include "cc/surfaces/surface_info.h"
 #include "cc/surfaces/surface_reference_factory.h"
 #include "ui/gfx/geometry/size.h"
 
 namespace cc {
 
 // A layer that renders a surface referencing the output of another compositor
 // instance or client.
 class CC_EXPORT SurfaceLayer : public Layer {
  public:
   static scoped_refptr<SurfaceLayer> Create(
       scoped_refptr<SurfaceReferenceFactory> ref_factory);
 
   void SetSurfaceInfo(const SurfaceInfo& surface_info);
 
+  // The current |surface_info_| becomes the |fallback_surface_info_| and the
+  // reference to the current fallback is removed.
+  void SwapSurfaceInfo(const SurfaceInfo& surface_info);
+
   // When stretch_content_to_fill_bounds is true, the scale of the embedded
   // surface is ignored and the content will be stretched to fill the bounds.
   void SetStretchContentToFillBounds(bool stretch_content_to_fill_bounds);
 
   // Layer overrides.
   std::unique_ptr<LayerImpl> CreateLayerImpl(LayerTreeImpl* tree_impl) override;
   void SetLayerTreeHost(LayerTreeHost* host) override;
   void PushPropertiesTo(LayerImpl* layer) override;
 
   scoped_refptr<SurfaceReferenceFactory> surface_reference_factory() const {
     return ref_factory_;
   }
-  const SurfaceInfo& surface_info() const { return surface_info_; }
+
+  const SurfaceInfo& primary_surface_info() const {
+    return primary_surface_info_;
+  }
+
+  const SurfaceInfo& fallback_surface_info() const {
+    return fallback_surface_info_;
+  }
 
  protected:
   explicit SurfaceLayer(scoped_refptr<SurfaceReferenceFactory> ref_factory);
   bool HasDrawableContent() const override;
 
  private:
   ~SurfaceLayer() override;
-  void RemoveCurrentReference();
+  void RemoveReference(base::Closure reference_returner);
 
-  SurfaceInfo surface_info_;
+  SurfaceInfo primary_surface_info_;
+  base::Closure primary_reference_returner_;
+
+  SurfaceInfo fallback_surface_info_;
+  base::Closure fallback_reference_returner_;
+
   scoped_refptr<SurfaceReferenceFactory> ref_factory_;
-  base::Closure reference_returner_;
   bool stretch_content_to_fill_bounds_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(SurfaceLayer);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_SURFACE_LAYER_H_