Adds an interface to SurfaceHittestDelegate in order to override

cc/surfaces/surface_hittest.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/surfaces/surface_hittest.h"
 
 #include "cc/output/compositor_frame.h"
 #include "cc/output/delegated_frame_data.h"
 #include "cc/quads/draw_quad.h"
 #include "cc/quads/render_pass_draw_quad.h"
@@ skipping 86 matching lines @@
       const SurfaceDrawQuad* surface_quad = SurfaceDrawQuad::MaterialCast(quad);
 
       if (delegate_ &&
           delegate_->RejectHitTarget(surface_quad, point_in_quad_space)) {
         continue;
       }
 
       gfx::Transform transform_to_child_space;
       if (GetTargetSurfaceAtPointInternal(
               surface_quad->surface_id, RenderPassId(), point_in_quad_space,
-              referenced_passes, out_surface_id, &transform_to_child_space)) {
+              referenced_passes, out_surface_id, &transform_to_child_space) ||
+          (delegate_ &&
+           delegate_->AcceptHitTarget(surface_quad, point_in_quad_space))) {
+        *out_surface_id = surface_quad->surface_id;
         *out_transform = transform_to_child_space * target_to_quad_transform *
                          transform_from_root_target;
         return true;
       }
 
       continue;
     }
 
     if (quad->material == DrawQuad::RENDER_PASS) {
       // We've hit a RenderPassDrawQuad, we need to recurse into this
@@ skipping 148 matching lines @@
     return false;
   }
 
   *point_in_quad_space = point_in_render_pass_space;
   target_to_quad_transform->TransformPoint(point_in_quad_space);
 
   return quad->rect.Contains(*point_in_quad_space);
 }
 
 }  // namespace cc