Preliminary compositor disabling patch.

cc/output/overlay_strategy_single_on_top.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 "cc/output/overlay_strategy_single_on_top.h"
 
 #include <limits>
 
 #include "cc/quads/draw_quad.h"
 #include "cc/quads/solid_color_draw_quad.h"
@@ skipping 169 matching lines @@
   // Add the overlay.
   candidate.plane_z_order = 1;
   candidates.push_back(candidate);
 
   // Check for support.
   capability_checker_->CheckOverlaySupport(&candidates);
 
   // If the candidate can be handled by an overlay, create a pass for it.
   if (candidates[1].overlay_handled) {
     quad_list.EraseAndInvalidateAllPointers(candidate_iterator);
+    root_render_pass->overlay_rect = gfx::Rect();
+    for (const auto* quad : root_render_pass->quad_list) {
+      if (quad->damaged) {
+        gfx::RectF rect = gfx::RectF(quad->visible_rect);
+        quad->quadTransform().TransformRect(&rect);
+        root_render_pass->overlay_rect.Union(gfx::ToEnclosingRect(rect));
+      }
+    }
     candidate_list->swap(candidates);
     return true;
   }
   return false;
 }
 
 }  // namespace cc