Only Record Ugliness Histogram for Compositor Side Changes

cc/trees/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_TREES_LAYER_TREE_IMPL_H_
 #define CC_TREES_LAYER_TREE_IMPL_H_
 
 #include <list>
 #include <string>
 #include <vector>
@@ skipping 170 matching lines @@
   }
   bool needs_update_draw_properties() const {
     return needs_update_draw_properties_;
   }
 
   void set_needs_full_tree_sync(bool needs) { needs_full_tree_sync_ = needs; }
   bool needs_full_tree_sync() const { return needs_full_tree_sync_; }
 
   void ForceRedrawNextActivation() { next_activation_forces_redraw_ = true; }
 
+  void increment_frames_have_been_drawn() {
+    if (frames_have_been_drawn_)

[weiliangc, 2014/07/22 22:01:13]

I use this check to make sure if TreeLayerImpl if has never been updated from
main thread, we are not going to count frames, and consequently not tracking
histogram info.

Is there a better way to achieve this?

[enne (OOO), 2014/07/22 22:35:38]

I'm not sure what you're worried about here.  If a LayerTreeImpl has never been
updated, then it won't have a root layer and can't draw.  (Is this a concrete
issue that you're running into or a more theoretical worry?)

I think you could make your variable a boolean "has_ever_been_drawn" and it'd be
more clear.

+      ++frames_have_been_drawn_;
+  }
+  int frames_have_been_drawn() const { return frames_have_been_drawn_; }
+
   void set_ui_resource_request_queue(const UIResourceRequestQueue& queue);
 
   const LayerImplList& RenderSurfaceLayerList() const;
 
   // These return the size of the root scrollable area and the size of
   // the user-visible scrolling viewport, in CSS layout coordinates.
   gfx::Size ScrollableSize() const;
   gfx::SizeF ScrollableViewportSize() const;
 
   gfx::Rect RootScrollLayerDeviceViewportBounds() const;
@@ skipping 122 matching lines @@
   bool requires_high_res_to_draw_;
   bool viewport_size_invalid_;
   bool needs_update_draw_properties_;
 
   // In impl-side painting mode, this is true when the tree may contain
   // structural differences relative to the active tree.
   bool needs_full_tree_sync_;
 
   bool next_activation_forces_redraw_;
 
+  int frames_have_been_drawn_;

[weiliangc, 2014/07/22 22:01:13]

I'm not very happy about this variable name but not sure what else to call it?

+
   ScopedPtrVector<SwapPromise> swap_promise_list_;
 
   UIResourceRequestQueue ui_resource_request_queue_;
 
   int render_surface_layer_list_id_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(LayerTreeImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_IMPL_H_