cc: Build Image to Region map during image meta-data generation.

cc/playback/display_item_list.cc

Index: cc/playback/display_item_list.cc
diff --git a/cc/playback/display_item_list.cc b/cc/playback/display_item_list.cc
index 068cb00999b665bedd8d587cef4a66c2fe128a66..42011949c3497956ce33762d371ba7cbdf6d0836 100644
--- a/cc/playback/display_item_list.cc
+++ b/cc/playback/display_item_list.cc
@@ -271,4 +271,8 @@ void DisplayItemList::GetDiscardableImagesInRect(
   image_map_.GetDiscardableImagesInRect(rect, raster_scales, images);
 }
 
+Region DisplayItemList::GetRegionForImage(uint32_t image_id) {
+  return image_map_.GetRegionForImage(image_id);
+}
+
 }  // namespace cc