Add command-line flag to force compositor framerate.

ui/compositor/compositor.h

 // Copyright (c) 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.
 
 #ifndef UI_COMPOSITOR_COMPOSITOR_H_
 #define UI_COMPOSITOR_COMPOSITOR_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 384 matching lines @@
   base::ObserverList<CompositorObserver, true> observer_list_;
   base::ObserverList<CompositorAnimationObserver> animation_observer_list_;
 
   gfx::AcceleratedWidget widget_ = gfx::kNullAcceleratedWidget;
   // A sequence number of a current compositor frame for use with metrics.
   int activated_frame_count_ = 0;
 
   // Current vsync refresh rate per second.
   float refresh_rate_ = 0.f;
 
+  // If nonzero, this is the refresh rate forced from the command-line.
+  double forced_refresh_rate_ = 0.f;
+
   // A map from child id to parent id.
   std::unordered_set<cc::FrameSinkId, cc::FrameSinkIdHash> child_frame_sinks_;
   bool widget_valid_ = false;
   bool compositor_frame_sink_requested_ = false;
   const cc::FrameSinkId frame_sink_id_;
   scoped_refptr<cc::Layer> root_web_layer_;
   std::unique_ptr<cc::AnimationHost> animation_host_;
   std::unique_ptr<cc::LayerTreeHost> host_;
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
 
@@ skipping 20 matching lines @@
 
   base::WeakPtrFactory<Compositor> weak_ptr_factory_;
   base::WeakPtrFactory<Compositor> lock_timeout_weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Compositor);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_COMPOSITOR_H_