cc: Make SingleOnTop strategy reject transformed overlays.

cc/output/overlay_strategy_single_on_top.cc

Index: cc/output/overlay_strategy_single_on_top.cc
diff --git a/cc/output/overlay_strategy_single_on_top.cc b/cc/output/overlay_strategy_single_on_top.cc
index ecc400972df08c93b2de6383dd46e324f192ee0d..75a31a2c1cca227e2e1d75b3a227561d0eb8b11d 100644
--- a/cc/output/overlay_strategy_single_on_top.cc
+++ b/cc/output/overlay_strategy_single_on_top.cc
@@ -39,6 +39,10 @@ bool OverlayStrategySingleOnTop::TryOverlay(
     OverlayCandidateList* candidate_list,
     const OverlayCandidate& candidate,
     QuadList::Iterator candidate_iterator) {
+  // Reject transformed overlays.
+  // TODO(dcastagna): Remove this once drm platform supports transforms.
+  if (candidate.transform != gfx::OVERLAY_TRANSFORM_NONE)
+    return false;
   // Check that no prior quads overlap it.
   if (OverlayCandidate::IsOccluded(candidate, quad_list->cbegin(),
                                    candidate_iterator))