cc: Partial tile update for one-copy raster.

cc/tiles/picture_layer_tiling.h

Index: cc/tiles/picture_layer_tiling.h
diff --git a/cc/tiles/picture_layer_tiling.h b/cc/tiles/picture_layer_tiling.h
index 7726f32085c8b86fc2abcf4c9a8f8ff78a760e9c..fb0307bdf643bfb77362daa267538962b6578a06 100644
--- a/cc/tiles/picture_layer_tiling.h
+++ b/cc/tiles/picture_layer_tiling.h
@@ -276,8 +276,9 @@ class CC_EXPORT PictureLayerTiling {
   void SetLiveTilesRect(const gfx::Rect& live_tiles_rect);
   void VerifyLiveTilesRect(bool is_on_recycle_tree) const;
   Tile* CreateTile(int i, int j);
-  // Returns true if the Tile existed and was removed from the tiling.
-  bool RemoveTileAt(int i, int j);
+  // Returns true if the Tile existed and was removed from the tiling. If true,
+  // and |id| is not null, sets |id| to that of the removed Tile.
+  bool RemoveTileAt(int i, int j, Tile::Id* id);

[reveman, 2015/05/28 05:07:25]

adding an 'id' output param seems a bit too specific for the exact usage of this
patch. I think it would be nicer to add an alternative TakeTileAt function that
allows you to get the id when needed and the existing RemoveTileAt function can
simply be implemented on top of it.

[danakj, 2015/05/28 18:54:47]

I think we're making perfect the enemy of the good.

Done. I didn't make RemoveTileAt use TakeTileAt. That would just be more pointer
moving around for no use.

   bool TilingMatchesTileIndices(const PictureLayerTiling* twin) const;
 
   // Computes a skewport. The calculation extrapolates the last visible