cc: Change the restrictions on overlays for video

cc/output/overlay_candidate.h

Index: cc/output/overlay_candidate.h
diff --git a/cc/output/overlay_candidate.h b/cc/output/overlay_candidate.h
index 9a1e534e5f23591c9812fb8d28746b67e12ed7bb..28ae8cb73d35897979db66e61e3ac5bd720069a8 100644
--- a/cc/output/overlay_candidate.h
+++ b/cc/output/overlay_candidate.h
@@ -20,6 +20,10 @@ class CC_EXPORT OverlayCandidate {
   static gfx::OverlayTransform GetOverlayTransform(
       const gfx::Transform& quad_transform,
       bool flipped);
+  // Apply transform |delta| to |in| and return the resulting transform,
+  // or OVERLAY_TRANSFORM_INVALID.
+  static gfx::OverlayTransform ModifyTransform(gfx::OverlayTransform in,
+                                               gfx::OverlayTransform delta);
   static gfx::Rect GetOverlayRect(const gfx::Transform& quad_transform,
                                   const gfx::Rect& rect);