Implement on demand quad rasterization for PicturePiles.

cc/resources/managed_tile_state.h

Index: cc/resources/managed_tile_state.h
diff --git a/cc/resources/managed_tile_state.h b/cc/resources/managed_tile_state.h
index 3452da75afaf10fe3d7b43ce3670245e42c67fb0..a1b596f314dd390d6c9ed982520eaa348a2ddfae 100644
--- a/cc/resources/managed_tile_state.h
+++ b/cc/resources/managed_tile_state.h
@@ -67,6 +67,10 @@ class CC_EXPORT ManagedTileState {
       friend class TileManager;
       friend class ManagedTileState;
 
+      void set_texture() {
+        mode_ = TEXTURE_MODE;
+      }
+
       void set_transparent() {
         mode_ = TRANSPARENT_MODE;
       }
@@ -76,6 +80,10 @@ class CC_EXPORT ManagedTileState {
         solid_color_ = color;
       }
 
+      void set_rasterize_on_demand() {
+        mode_ = PICTURE_PILE_MODE;
+      }
+
       Mode mode_;
       SkColor solid_color_;