[cc] Fix CompositorFrameSinkSupport BeginFrameAck interface.

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 49 matching lines @@
 
 void CompositorFrameSinkSupport::EvictFrame() {
   surface_factory_.EvictSurface();
 }
 
 void CompositorFrameSinkSupport::SetNeedsBeginFrame(bool needs_begin_frame) {
   needs_begin_frame_ = needs_begin_frame;
   UpdateNeedsBeginFramesInternal();
 }
 
-void CompositorFrameSinkSupport::DidFinishFrame(const BeginFrameAck& ack) {
+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.
+  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.
+  // See https://crbug.com/703079.
+  if (begin_frame_source_)
+    begin_frame_source_->DidFinishFrame(this, frame.metadata.begin_frame_ack);
 }
 
 void CompositorFrameSinkSupport::UpdateSurfaceReferences(
     const SurfaceId& last_surface_id,
     const LocalSurfaceId& local_surface_id) {
   const bool surface_id_changed =
       last_surface_id.local_surface_id() != local_surface_id;
 
   // If this is a display root surface and the SurfaceId is changing, make the
   // new SurfaceId reachable from the top-level root.
@@ skipping 137 matching lines @@
   else
     begin_frame_source_->RemoveObserver(this);
 }
 
 void CompositorFrameSinkSupport::RequestCopyOfSurface(
     std::unique_ptr<CopyOutputRequest> request) {
   surface_factory_.RequestCopyOfSurface(std::move(request));
 }
 
 }  // namespace cc