cc: Invalidate framebuffer contents when clearing

cc/trees/layer_tree_host.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_H_
 #define CC_TREES_LAYER_TREE_HOST_H_
 
 #include <limits>
 #include <list>
 #include <vector>
@@ skipping 65 matching lines @@
   unsigned best_texture_format;
   bool using_partial_swap;
   bool using_set_visibility;
   bool using_egl_image;
   bool allow_partial_texture_updates;
   bool using_offscreen_context3d;
   int max_texture_size;
   bool avoid_pow2_textures;
   bool using_map_image;
   bool using_shared_memory_resources;
+  bool using_discard_framebuffer;
 };
 
 struct CC_EXPORT UIResourceRequest {
   enum UIResourceRequestType {
     UIResourceCreate,
     UIResourceDelete,
     UIResourceInvalidRequest
   };
 
   UIResourceRequest();
@@ skipping 322 matching lines @@
   };
   LCDTextMetrics lcd_text_metrics_;
   int tree_id_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHost);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_H_