cc: Remove unused fields originally used for RenderingStats collection

cc/trees/layer_tree_host_impl.h

Index: cc/trees/layer_tree_host_impl.h
diff --git a/cc/trees/layer_tree_host_impl.h b/cc/trees/layer_tree_host_impl.h
index 08ade52442b3044bd7a24a1a5c4dce154fa9ae78..520fc90c7684be09698cd76bfd858808fc666fd6 100644
--- a/cc/trees/layer_tree_host_impl.h
+++ b/cc/trees/layer_tree_host_impl.h
@@ -453,13 +453,6 @@ class CC_EXPORT LayerTreeHostImpl : public InputHandlerClient,
   scoped_ptr<MemoryHistory> memory_history_;
   scoped_ptr<DebugRectHistory> debug_rect_history_;
 
-  int64 num_impl_thread_scrolls_;
-  int64 num_main_thread_scrolls_;
-
-  int64 cumulative_num_layers_drawn_;
-
-  int64 cumulative_num_missing_tiles_;
-
   // The maximum memory that would be used by the prioritized resource
   // manager, if there were no limit on memory usage.
   size_t max_memory_needed_bytes_;