[#2] Pass gfx structs by const ref (gfx::Rect, gfx::RectF)

cc/resources/priority_calculator.h

 // Copyright 2010 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_RESOURCES_PRIORITY_CALCULATOR_H_
 #define CC_RESOURCES_PRIORITY_CALCULATOR_H_
 
 #include "base/basictypes.h"
 #include "cc/base/cc_export.h"
 
 namespace gfx { class Rect; }
 
 namespace cc {
 
 class CC_EXPORT PriorityCalculator {
  public:
   PriorityCalculator() {}
 
   static int UIPriority(bool draws_to_root_surface);
   static int VisiblePriority(bool draws_to_root_surface);
   static int RenderSurfacePriority();
   static int LingeringPriority(int previous_priority);
-  static int PriorityFromDistance(gfx::Rect visible_rect,
-                                  gfx::Rect texture_rect,
+  static int PriorityFromDistance(const gfx::Rect& visible_rect,
+                                  const gfx::Rect& texture_rect,
                                   bool draws_to_root_surface);
   static int SmallAnimatedLayerMinPriority();
 
   static int HighestPriority();
   static int LowestPriority();
   static inline bool priority_is_lower(int a, int b) { return a > b; }
   static inline bool priority_is_higher(int a, int b) { return a < b; }
   static inline int max_priority(int a, int b) {
     return priority_is_higher(a, b) ? a : b;
   }
 
   static int AllowNothingCutoff();
   static int AllowVisibleOnlyCutoff();
   static int AllowVisibleAndNearbyCutoff();
   static int AllowEverythingCutoff();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PriorityCalculator);
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_PRIORITY_CALCULATOR_H_