Mac Overlays: Add AllOrNothing strategy

cc/output/overlay_strategy_sandwich.cc

 // Copyright 2015 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 "cc/output/overlay_strategy_sandwich.h"
 
 #include "cc/base/math_util.h"
 #include "cc/base/region.h"
 #include "cc/output/overlay_candidate_validator.h"
 #include "cc/quads/draw_quad.h"
@@ skipping 99 matching lines @@
                                     1.f / pixel_bounds.height());
     main_image_on_top.plane_z_order = 2;
     main_image_on_top.transform = gfx::OVERLAY_TRANSFORM_NONE;
     main_image_on_top.use_output_surface_for_resource = true;
     new_candidate_list.push_back(main_image_on_top);
   }
 
   // Check for support.
   capability_checker->CheckOverlaySupport(&new_candidate_list);
   for (const OverlayCandidate& candidate : new_candidate_list) {
-    if (candidate.plane_z_order > 0 && !candidate.overlay_handled)
+    if (!candidate.overlay_handled)
       return DID_NOT_CREATE_OVERLAY;
   }
 
   // Remove the quad for the overlay quad. Replace it with a transparent quad
   // if we're putting a new overlay on top.
   if (pixel_covered_rects.empty()) {
     *candidate_iter_in_quad_list =
         quad_list.EraseAndInvalidateAllPointers(*candidate_iter_in_quad_list);
   } else {
     // Cache the information from the candidate quad that we'll need to
@@ skipping 23 matching lines @@
                                SK_ColorTRANSPARENT, true);
       ++(*candidate_iter_in_quad_list);
     }
   }
 
   candidate_list->swap(new_candidate_list);
   return CREATED_OVERLAY_KEEP_LOOKING;
 }
 
 }  // namespace cc