cc: Introduce BeginFrame sequence numbers and acknowledgements.

cc/blimp/layer_tree_host_remote.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_BLIMP_LAYER_TREE_HOST_REMOTE_H_
 #define CC_BLIMP_LAYER_TREE_HOST_REMOTE_H_
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "cc/base/cc_export.h"
@@ skipping 104 matching lines @@
 
  private:
   enum class FramePipelineStage { NONE, ANIMATE, UPDATE_LAYERS, COMMIT };
 
   void MainFrameRequested(FramePipelineStage requested_pipeline_stage);
   void ScheduleMainFrameIfNecessary();
   void MainFrameComplete();
   void SerializeCurrentState(proto::LayerTreeHost* layer_tree_host_proto);
 
   const int id_;
   int source_frame_number_ = 0;

[Sami, 2016/12/06 12:41:06]

aside: We might want to drop a TODO somewhere about replacing this with
begin_frame_number_ since I think it fills a similar use.

[Eric Seckler, 2016/12/06 17:33:59]

In general, the LayerTreeHost::SourceFrameNumber() seems to be incremented for
new main frames, rather than a BeginFrame. For LTHRemote that turns out to be
the same as the BeginFrame number used for its BeginFrameArgs creation, but
sign/width of the number are different - which is why I added another field. I'm
adding a TODO to the LTH interface to think about using BeginFrame numbers
instead of "source" frame numbers.

[Sami, 2016/12/07 16:59:39]

True, I was just thinking that since the only way to get a new main frame is via
a BeginFrame, so another counter doesn't really add any new information --
unless we want main frame numbers to be consecutive for some reason. In any case
I think we can defer this decision.

   bool visible_ = false;
   bool defer_commits_ = false;
+  uint64_t begin_frame_number_ = 0;
 
   // In threaded/single-threaded mode, the LayerTree and Layers expect scroll/
   // scale updates to come from the impl thread only during the main frame.
   // Since we synchronize state outside of that, this is set so we can
   // temporarily report that a commit is in progress.
   bool synchronizing_client_updates_ = false;
 
   // Set to true if a main frame request is pending on the
   // RemoteCompositorBridge.
   bool main_frame_requested_from_bridge_ = false;
@@ skipping 32 matching lines @@
   SurfaceSequenceGenerator surface_sequence_generator_;
 
   base::WeakPtr<InputHandler> input_handler_weak_ptr_;
 
   base::WeakPtrFactory<LayerTreeHostRemote> weak_factory_;
 };
 
 }  // namespace cc
 
 #endif  // CC_BLIMP_LAYER_TREE_HOST_REMOTE_H_