Record histogram when succeeding in creating a DC layer overlay.

cc/output/dc_layer_overlay.cc

 // Copyright 2017 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/dc_layer_overlay.h"
 
 #include "base/metrics/histogram_macros.h"
 #include "cc/base/math_util.h"
 #include "cc/quads/solid_color_draw_quad.h"
 #include "cc/quads/yuv_video_draw_quad.h"
@@ skipping 187 matching lines @@
         }
       } else {
         // Entire replacement quad must be redrawn.
         damage_rect->Union(quad_rectangle);
       }
       previous_occlusion_bounding_box_ =
           gfx::ToEnclosingRect(occlusion_bounding_box);
     }
     overlay_damage_rect->Union(quad_rectangle);
 
+    RecordDCLayerResult(DC_LAYER_SUCCESS);
     ca_layer_overlays->push_back(ca_layer);
     // Only allow one overlay for now.
     break;
   }
   damage_rect->Intersect(gfx::ToEnclosingRect(display_rect));
   previous_frame_underlay_rect_ = this_frame_underlay_rect;
   previous_display_rect_ = display_rect;
 }
 
 }  // namespace cc