cc: Ensure that skewport.Contains(visible_rect) is always true.

cc/tiles/picture_layer_tiling.cc

Index: cc/tiles/picture_layer_tiling.cc
diff --git a/cc/tiles/picture_layer_tiling.cc b/cc/tiles/picture_layer_tiling.cc
index 8db23522e6bfe11783d8dabc98dad573cbca83ca..3ae1ad97e53abdab385a36508dba801b724049da 100644
--- a/cc/tiles/picture_layer_tiling.cc
+++ b/cc/tiles/picture_layer_tiling.cc
@@ -552,6 +552,13 @@ gfx::Rect PictureLayerTiling::ComputeSkewport(
   // union in case intersecting would have left the empty rect.
   skewport.Intersect(max_skewport);
 
+  // Due to limits in int's representation, it is possible that the two
+  // operations above (union and intersect) result in an empty skewport. To
+  // avoid any unpleasant situations like that, union the visible rect again to
+  // ensure that skewport.Contains(visible_rect_in_content_space) is always
+  // true.
+  skewport.Union(visible_rect_in_content_space);
+
   return skewport;
 }