Force use of and cache render surface.

cc/trees/draw_property_utils.cc

Index: cc/trees/draw_property_utils.cc
diff --git a/cc/trees/draw_property_utils.cc b/cc/trees/draw_property_utils.cc
index 15535c53448ed3030494b59e025a7dccaada694f..98f8d002f67d60fa0ef33baa22f68fc9eb962892 100644
--- a/cc/trees/draw_property_utils.cc
+++ b/cc/trees/draw_property_utils.cc
@@ -555,9 +555,13 @@ static void SetSurfaceIsClipped(const ClipTree& clip_tree,
     is_clipped = false;
   } else if (render_surface->ClipTreeIndex() ==
              render_surface->render_target()->ClipTreeIndex()) {
-    // There is no clip between between the render surface and its target, so
+    // There is no clip between the render surface and its target, so
     // the surface need not be clipped.
     is_clipped = false;
+  } else if (render_surface->ForceRenderSurface()) {
+    // Avoid clipping when force use of render surface. We might need the whole
+    // surface during some animations.
+    is_clipped = false;
   } else {
     // If the clips between the render surface and its target only expand the
     // clips and do not apply any new clip, we need not clip the render surface.