[cc] Remove remaining_frames from BeginFrameAck.

cc/surfaces/compositor_frame_sink_support.cc

 // 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.
 
 #include "cc/surfaces/compositor_frame_sink_support.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "cc/output/compositor_frame.h"
@@ skipping 57 matching lines @@
 }
 
 void CompositorFrameSinkSupport::BeginFrameDidNotSwap(
     const BeginFrameAck& ack) {
   // TODO(eseckler): While a pending CompositorFrame exists (see TODO below), we
   // should not acknowledge immediately. Instead, we should update the ack that
   // will be sent to DisplayScheduler when the pending frame is activated.
   DCHECK_LE(BeginFrameArgs::kStartingFrameNumber, ack.sequence_number);
   // |has_damage| is not transmitted, but false by default.
   DCHECK(!ack.has_damage);
-  // |remaining_frames| is not transmitted, but 0 by default.
-  DCHECK_EQ(0u, ack.remaining_frames);
   if (begin_frame_source_)
     begin_frame_source_->DidFinishFrame(this, ack);
 }
 
 void CompositorFrameSinkSupport::SubmitCompositorFrame(
     const LocalSurfaceId& local_surface_id,
     CompositorFrame frame) {
   ++ack_pending_count_;
 
   if (frame.metadata.begin_frame_ack.sequence_number <
       BeginFrameArgs::kStartingFrameNumber) {
     DLOG(ERROR) << "Received CompositorFrame with invalid BeginFrameAck.";
     frame.metadata.begin_frame_ack.source_id = BeginFrameArgs::kManualSourceId;
     frame.metadata.begin_frame_ack.sequence_number =
         BeginFrameArgs::kStartingFrameNumber;
   }
-  // |has_damage| and |remaining_frames| are not transmitted.
+  // |has_damage| is not transmitted.
   frame.metadata.begin_frame_ack.has_damage = true;
-  frame.metadata.begin_frame_ack.remaining_frames = 0;
 
   surface_factory_.SubmitCompositorFrame(
       local_surface_id, std::move(frame),
       base::Bind(&CompositorFrameSinkSupport::DidReceiveCompositorFrameAck,
                  weak_factory_.GetWeakPtr()));
 
   // TODO(eseckler): The CompositorFrame submitted below might not be activated
   // right away b/c of surface synchronization. We should only send the
   // BeginFrameAck to DisplayScheduler when it is activated. This also means
   // that we need to stay an active BFO while a CompositorFrame is pending.
@@ skipping 150 matching lines @@
   else
     begin_frame_source_->RemoveObserver(this);
 }
 
 void CompositorFrameSinkSupport::RequestCopyOfSurface(
     std::unique_ptr<CopyOutputRequest> request) {
   surface_factory_.RequestCopyOfSurface(std::move(request));
 }
 
 }  // namespace cc