Get rid of virtual Display::CreateScheduler.

cc/scheduler/begin_frame_source.h

 // 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.
 
 #ifndef CC_SCHEDULER_BEGIN_FRAME_SOURCE_H_
 #define CC_SCHEDULER_BEGIN_FRAME_SOURCE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 96 matching lines @@
   // is pending at a time.
   virtual void DidFinishFrame(BeginFrameObserver* obs,
                               size_t remaining_frames) = 0;
 
   // Add/Remove an observer from the source. When no observers are added the BFS
   // should shut down its timers, disable vsync, etc.
   virtual void AddObserver(BeginFrameObserver* obs) = 0;
   virtual void RemoveObserver(BeginFrameObserver* obs) = 0;
 };
 
+// A BeginFrameSource that does nothing.
+class StubBeginFrameSource : public BeginFrameSource {
+ public:
+  void DidFinishFrame(BeginFrameObserver* obs,
+                      size_t remaining_frames) override {}
+  void AddObserver(BeginFrameObserver* obs) override {}
+  void RemoveObserver(BeginFrameObserver* obs) override {}
+};
+
 // A frame source which ticks itself independently.
 class CC_EXPORT SyntheticBeginFrameSource : public BeginFrameSource {
  public:
   ~SyntheticBeginFrameSource() override;
 
   virtual void OnUpdateVSyncParameters(base::TimeTicks timebase,
                                        base::TimeDelta interval) = 0;
   // This overrides any past or future interval from updating vsync parameters.
   virtual void SetAuthoritativeVSyncInterval(base::TimeDelta interval) = 0;
 };
@@ skipping 61 matching lines @@
   std::unordered_set<BeginFrameObserver*> observers_;
   base::TimeTicks last_timebase_;
   base::TimeDelta authoritative_interval_;
 
   DISALLOW_COPY_AND_ASSIGN(DelayBasedBeginFrameSource);
 };
 
 }  // namespace cc
 
 #endif  // CC_SCHEDULER_BEGIN_FRAME_SOURCE_H_