Remove "mixin" from BeginFrameSource/Observer base classes.

cc/test/scheduler_test_common.cc

 // Copyright 2012 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/scheduler_test_common.h"
 
 #include <string>
 
 #include "base/logging.h"
 
@@ skipping 22 matching lines @@
 
 TestDelayBasedTimeSource::~TestDelayBasedTimeSource() {
 }
 
 void FakeBeginFrameSource::DidFinishFrame(size_t remaining_frames) {
   remaining_frames_ = remaining_frames;
 }
 void FakeBeginFrameSource::AsValueInto(
     base::trace_event::TracedValue* dict) const {
   dict->SetString("type", "FakeBeginFrameSource");
-  BeginFrameSourceMixIn::AsValueInto(dict);
+  BeginFrameSourceBase::AsValueInto(dict);
 }
 
 TestBackToBackBeginFrameSource::TestBackToBackBeginFrameSource(
     scoped_refptr<TestNowSource> now_src,
     base::SingleThreadTaskRunner* task_runner)
     : BackToBackBeginFrameSource(task_runner), now_src_(now_src) {
 }
 
 TestBackToBackBeginFrameSource::~TestBackToBackBeginFrameSource() {
 }
@@ skipping 74 matching lines @@
 }
 
 base::TimeTicks TestScheduler::Now() const {
   return now_src_->Now();
 }
 
 TestScheduler::~TestScheduler() {
 }
 
 }  // namespace cc