[cc] Add and use BeginFrameAck for DidFinishFrame.

cc/test/fake_external_begin_frame_source.cc

 // Copyright 2014 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/test/fake_external_begin_frame_source.h"
 
 #include "base/location.h"
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
@@ skipping 23 matching lines @@
   }
 }
 
 void FakeExternalBeginFrameSource::AddObserver(BeginFrameObserver* obs) {
   DCHECK(obs);
   DCHECK(observers_.find(obs) == observers_.end());
 
   bool observers_was_empty = observers_.empty();
   observers_.insert(obs);
   obs->OnBeginFrameSourcePausedChanged(paused_);
-  if (observers_was_empty && tick_automatically_)
+  if (observers_was_empty && tick_automatically_) {
     PostTestOnBeginFrame();
+  } else if (current_args_.IsValid()) {
+    const BeginFrameArgs& last_args = obs->LastUsedBeginFrameArgs();
+    if (!last_args.IsValid() ||
+        last_args.frame_time < current_args_.frame_time) {
+      current_args_.type = BeginFrameArgs::MISSED;
+      obs->OnBeginFrame(current_args_);
+    }
+  }
   if (client_)
     client_->OnAddObserver(obs);
 }
 
 void FakeExternalBeginFrameSource::RemoveObserver(BeginFrameObserver* obs) {
   DCHECK(obs);
   DCHECK(observers_.find(obs) != observers_.end());
 
   observers_.erase(obs);
   if (observers_.empty())
     begin_frame_task_.Cancel();
   if (client_)
     client_->OnRemoveObserver(obs);
 }
 
 bool FakeExternalBeginFrameSource::IsThrottled() const {
   return true;
 }
 
 void FakeExternalBeginFrameSource::TestOnBeginFrame(
     const BeginFrameArgs& args) {
   DCHECK(CalledOnValidThread());
-  BeginFrameArgs modified_args = args;
-  modified_args.source_id = source_id();
-  modified_args.sequence_number = next_begin_frame_number_++;
+  current_args_ = args;
+  current_args_.source_id = source_id();
+  current_args_.sequence_number = next_begin_frame_number_++;
   std::set<BeginFrameObserver*> observers(observers_);
   for (auto* obs : observers)
-    obs->OnBeginFrame(modified_args);
+    obs->OnBeginFrame(current_args_);
   if (tick_automatically_)
     PostTestOnBeginFrame();
 }
 
 void FakeExternalBeginFrameSource::PostTestOnBeginFrame() {
   begin_frame_task_.Reset(
       base::Bind(&FakeExternalBeginFrameSource::TestOnBeginFrame,
                  weak_ptr_factory_.GetWeakPtr()));
   base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
       FROM_HERE, base::Bind(begin_frame_task_.callback(),
                             CreateBeginFrameArgsForTesting(
                                 BEGINFRAME_FROM_HERE, source_id(),
                                 next_begin_frame_number_)),
       base::TimeDelta::FromMilliseconds(milliseconds_per_frame_));
   next_begin_frame_number_++;
 }
 
 }  // namespace cc