[cc] Remove BeginFrameAck from BFS::DidFinishFrame and update tests.

cc/surfaces/compositor_frame_sink_support.cc

Index: cc/surfaces/compositor_frame_sink_support.cc
diff --git a/cc/surfaces/compositor_frame_sink_support.cc b/cc/surfaces/compositor_frame_sink_support.cc
index 896536f039cf4966b2c4204acb4034780d7765e6..4ad7f2a239131536a692a085727bc0a86c015abc 100644
--- a/cc/surfaces/compositor_frame_sink_support.cc
+++ b/cc/surfaces/compositor_frame_sink_support.cc
@@ -86,15 +86,15 @@ void CompositorFrameSinkSupport::SetNeedsBeginFrame(bool needs_begin_frame) {
 }
 
 void CompositorFrameSinkSupport::DidNotProduceFrame(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_GE(ack.sequence_number, BeginFrameArgs::kStartingFrameNumber);
 
   // |has_damage| is not transmitted, but false by default.
   DCHECK(!ack.has_damage);
+
+  // TODO(eseckler): Forward |ack| via SurfaceObservers.
+
   if (begin_frame_source_)
-    begin_frame_source_->DidFinishFrame(this, ack);
+    begin_frame_source_->DidFinishFrame(this);

[sunnyps, 2017/05/24 02:38:25]

nit: We don't need this. When we use back to back BFS (disable vsync) we always
instantiate it in the client.

[Eric Seckler, 2017/05/24 09:00:40]

I think this isn't true for local clients. DirectCFS currently always exposes an
ExternalBFS to its client, not the original BackToBackBFS. Thus, CFSSupport
needs to ack to the BFS on behalf of such local clients. (And this will also be
true once we stop exposing BFSes to CompositorFrameSink(Client)s.)

 }
 
 void CompositorFrameSinkSupport::SubmitCompositorFrame(
@@ -102,16 +102,14 @@ void CompositorFrameSinkSupport::SubmitCompositorFrame(
     CompositorFrame frame) {
   TRACE_EVENT0("cc", "CompositorFrameSinkSupport::SubmitCompositorFrame");
   DCHECK(local_surface_id.is_valid());
-  DCHECK_GE(frame.metadata.begin_frame_ack.sequence_number,
-            BeginFrameArgs::kStartingFrameNumber);
   DCHECK(!frame.render_pass_list.empty());
 
   ++ack_pending_count_;
 
   // |has_damage| is not transmitted.
   frame.metadata.begin_frame_ack.has_damage = true;
-
   BeginFrameAck ack = frame.metadata.begin_frame_ack;
+  DCHECK_LE(BeginFrameArgs::kStartingFrameNumber, ack.sequence_number);
 
   if (!ui::LatencyInfo::Verify(frame.metadata.latency_info,
                                "RenderWidgetHostImpl::OnSwapCompositorFrame")) {
@@ -147,13 +145,10 @@ void CompositorFrameSinkSupport::SubmitCompositorFrame(
   }
   current_surface_ = std::move(surface);
 
-  // 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.
+  // TODO(eseckler): Forward |ack| via SurfaceObservers.
+
   if (begin_frame_source_)
-    begin_frame_source_->DidFinishFrame(this, ack);
+    begin_frame_source_->DidFinishFrame(this);

[sunnyps, 2017/05/24 02:38:25]

nit: same here

[Eric Seckler, 2017/05/24 09:00:40]

see above.

 }
 
 void CompositorFrameSinkSupport::UpdateSurfaceReferences(