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

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 48 matching lines @@
   DCHECK(obs);
   DCHECK(observers_.find(obs) != observers_.end());
 
   observers_.erase(obs);
   if (observers_.empty())
     begin_frame_task_.Cancel();
   if (client_)
     client_->OnRemoveObserver(obs);
 }
 
-void FakeExternalBeginFrameSource::DidFinishFrame(BeginFrameObserver* obs,
-                                                  const BeginFrameAck& ack) {
-  last_acks_[obs] = ack;
-}
+void FakeExternalBeginFrameSource::DidFinishFrame(BeginFrameObserver* obs) {}
 
 bool FakeExternalBeginFrameSource::IsThrottled() const {
   return true;
 }
 
 BeginFrameArgs FakeExternalBeginFrameSource::CreateBeginFrameArgs(
     BeginFrameArgs::CreationLocation location,
     base::SimpleTestTickClock* now_src) {
   return CreateBeginFrameArgsForTesting(location, source_id(),
                                         next_begin_frame_number_++, now_src);
@@ skipping 22 matching lines @@
                  weak_ptr_factory_.GetWeakPtr()));
   base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
       FROM_HERE,
       base::BindOnce(begin_frame_task_.callback(),
                      CreateBeginFrameArgs(BEGINFRAME_FROM_HERE)),
       base::TimeDelta::FromMilliseconds(milliseconds_per_frame_));
   next_begin_frame_number_++;
 }
 
 }  // namespace cc