Remove "mixin" from BeginFrameSource/Observer base classes.

cc/test/scheduler_test_common.h

 // Copyright 2011 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.
 
 #ifndef CC_TEST_SCHEDULER_TEST_COMMON_H_
 #define CC_TEST_SCHEDULER_TEST_COMMON_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 55 matching lines @@
                            OrderedSimpleTaskRunner* task_runner);
 
   // Overridden from DelayBasedTimeSource
   ~TestDelayBasedTimeSource() override;
   base::TimeTicks Now() const override;
   std::string TypeString() const override;
 
   scoped_refptr<TestNowSource> now_src_;
 };
 
-struct FakeBeginFrameSource : public BeginFrameSourceMixIn {
+struct FakeBeginFrameSource : public BeginFrameSourceBase {
   bool remaining_frames_ = false;
 
   BeginFrameObserver* GetObserver() { return observer_; }
 
   BeginFrameArgs TestLastUsedBeginFrameArgs() {
     if (observer_) {
       return observer_->LastUsedBeginFrameArgs();
     }
     return BeginFrameArgs();
   }
@@ skipping 124 matching lines @@
       const scoped_refptr<OrderedSimpleTaskRunner>& test_task_runner,
       TestSchedulerFrameSourcesConstructor* frame_sources_constructor,
       scoped_ptr<BeginFrameSource> external_begin_frame_source);
 
   scoped_refptr<TestNowSource> now_src_;
 };
 
 }  // namespace cc
 
 #endif  // CC_TEST_SCHEDULER_TEST_COMMON_H_