[Ozone] Fix SingleOnTop issue by checking if the quad is clipped.

ui/ozone/public/overlay_candidates_ozone.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/ozone/public/overlay_candidates_ozone.h"
 
 #include <stdlib.h>
 
 namespace ui {
 
-OverlayCandidatesOzone::OverlaySurfaceCandidate::OverlaySurfaceCandidate() {
-}
+OverlayCandidatesOzone::OverlaySurfaceCandidate::OverlaySurfaceCandidate()
+    : is_clipped(false) {}
 
 OverlayCandidatesOzone::OverlaySurfaceCandidate::~OverlaySurfaceCandidate() {
 }
 
 void OverlayCandidatesOzone::CheckOverlaySupport(
     OverlaySurfaceCandidateList* surfaces) {
   NOTREACHED();
 }
 
 OverlayCandidatesOzone::~OverlayCandidatesOzone() {
 }
 
 }  // namespace ui