cc: Don't pass simple well-defined classes by reference.

cc/trees/layer_tree_host_impl.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_TREES_LAYER_TREE_HOST_IMPL_H_
 #define CC_TREES_LAYER_TREE_HOST_IMPL_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 129 matching lines @@
     // RenderPassSink implementation.
     virtual void AppendRenderPass(scoped_ptr<RenderPass> render_pass) OVERRIDE;
   };
 
   virtual void BeginCommit();
   virtual void CommitComplete();
   virtual void Animate(base::TimeTicks monotonic_time,
                        base::Time wall_clock_time);
   virtual void UpdateAnimationState(bool start_ready_animations);
   void UpdateBackgroundAnimateTicking(bool should_background_tick);
-  void SetViewportDamage(const gfx::Rect& damage_rect);
+  void SetViewportDamage(gfx::Rect damage_rect);
 
   void ManageTiles();
   void SetAnticipatedDrawTime(base::TimeTicks time);
 
   // Returns false if problems occured preparing the frame, and we should try
   // to avoid displaying the frame. If PrepareToDraw is called, DidDrawAllLayers
   // must also be called, regardless of whether DrawLayers is called between the
   // two.
   virtual bool PrepareToDraw(FrameData* frame,
                              gfx::Rect device_viewport_damage_rect);
@@ skipping 310 matching lines @@
   scoped_ptr<AnimationRegistrar> animation_registrar_;
 
   RenderingStatsInstrumentation* rendering_stats_instrumentation_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_IMPL_H_