cc: Introduce BeginFrame sequence numbers and acknowledgements.

cc/trees/layer_tree_host.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 CC_TREES_LAYER_TREE_HOST_H_
 #define CC_TREES_LAYER_TREE_HOST_H_
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "cc/base/cc_export.h"
@@ skipping 28 matching lines @@
 // LayerTreeHostInProcess::CreateThreaded/CreateSingleThread to get either.
 class CC_EXPORT LayerTreeHost {
  public:
   virtual ~LayerTreeHost() {}
 
   // Returns the process global unique identifier for this LayerTreeHost.
   virtual int GetId() const = 0;
 
   // The current source frame number. This is incremented for each main frame
   // update(commit) pushed to the compositor thread.
+  // TODO(eseckler): Consider replacing this with BeginFrame sequence numbers.
   virtual int SourceFrameNumber() const = 0;
 
   // Returns the LayerTree that holds the main frame state pushed to the
   // LayerTreeImpl on commit.
   virtual LayerTree* GetLayerTree() = 0;
   virtual const LayerTree* GetLayerTree() const = 0;
 
   // Returns the UIResourceManager used to create UIResources for
   // UIResourceLayers pushed to the LayerTree.
   virtual UIResourceManager* GetUIResourceManager() const = 0;
@@ skipping 139 matching lines @@
   virtual void SetNextCommitWaitsForActivation() = 0;
 
   // The LayerTreeHost tracks whether the content is suitable for Gpu raster.
   // Calling this will reset it back to not suitable state.
   virtual void ResetGpuRasterizationTracking() = 0;
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_H_