cc: Throttle tile priority updates to once a frame.

cc/layer_tree_impl.h

 // Copyright 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 CC_LAYER_TREE_IMPL_H_
 #define CC_LAYER_TREE_IMPL_H_
 
 #include "base/hash_tables.h"
 #include "cc/layer_impl.h"
 
@@ skipping 95 matching lines @@
   SkColor background_color() const { return background_color_; }
   void set_background_color(SkColor color) { background_color_ = color; }
 
   bool has_transparent_background() const {
     return has_transparent_background_;
   }
   void set_has_transparent_background(bool transparent) {
     has_transparent_background_ = transparent;
   }
 
+  enum UpdateDrawPropertiesReason {
+    UPDATE_PENDING_TREE,
+    UPDATE_ACTIVE_TREE,
+    UPDATE_ACTIVE_TREE_FOR_DRAW
+  };
+
   // Updates draw properties and render surface layer list
-  void UpdateDrawProperties();
+  void UpdateDrawProperties(UpdateDrawPropertiesReason reason);
   void set_needs_update_draw_properties() {
     needs_update_draw_properties_ = true;
   }
   bool needs_update_draw_properties() const {
     return needs_update_draw_properties_;
   }
 
   void ClearRenderSurfaces();
 
   bool AreVisibleResourcesReady() const;
@@ skipping 45 matching lines @@
 
   bool contents_textures_purged_;
   bool needs_update_draw_properties_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeImpl);
 };
 
 }
 
 #endif  // CC_LAYER_TREE_IMPL_H_