Histogram to track missing and incomplete tiles

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 <list>
 #include <set>
 #include <string>
@@ skipping 578 matching lines @@
   // by the next sync from the main thread.
   scoped_ptr<LayerTreeImpl> recycle_tree_;
 
   InputHandlerClient* input_handler_client_;
   bool did_lock_scrolling_layer_;
   bool should_bubble_scrolls_;
   bool wheel_scrolling_;
   bool scroll_affects_scroll_handler_;
   int scroll_layer_id_when_mouse_over_scrollbar_;
 
+  bool is_scrolling_;
+
   bool tile_priorities_dirty_;
 
   // The optional delegate for the root layer scroll offset.
   LayerScrollOffsetDelegate* root_layer_scroll_offset_delegate_;
   LayerTreeSettings settings_;
   LayerTreeDebugState debug_state_;
   bool visible_;
   ManagedMemoryPolicy cached_managed_memory_policy_;
 
   gfx::Vector2dF accumulated_root_overscroll_;
@@ skipping 80 matching lines @@
   size_t transfer_buffer_memory_limit_;
 
   std::vector<PictureLayerImpl*> picture_layers_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_IMPL_H_