Canvas2d: Implement rerouting event by hit region's control.

third_party/WebKit/Source/modules/canvas2d/HitRegion.cpp

 // 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 "modules/canvas2d/HitRegion.h"
 
 #include "core/dom/AXObjectCache.h"
 #include "core/layout/LayoutBoxModelObject.h"
 
 namespace blink {
 
 HitRegion::HitRegion(const Path& path, const HitRegionOptions& options)
-    : m_id(options.id())
+    : m_id(options.id().isEmpty() ? String() : options.id())
     , m_control(options.control())
     , m_path(path)
 {
     if (options.fillRule() != "evenodd")
         m_fillRule = RULE_NONZERO;
     else
         m_fillRule = RULE_EVENODD;
 }
 
 bool HitRegion::contains(const FloatPoint& point) const
@@ skipping 111 matching lines @@
 DEFINE_TRACE(HitRegionManager)
 {
 #if ENABLE(OILPAN)
     visitor->trace(m_hitRegionList);
     visitor->trace(m_hitRegionIdMap);
     visitor->trace(m_hitRegionControlMap);
 #endif
 }
 
 } // namespace blink