clang/blink_gc_plugin: Replace 'WebCore' with 'blink'

tools/clang/blink_gc_plugin/tests/class_requires_finalization_mixin.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 "class_requires_finalization_mixin.h"
 
-namespace WebCore {
+namespace blink {
 
 void MixinFinalizable::trace(Visitor* visitor)
 {
     visitor->trace(m_onHeap);
 }
 
 void MixinNotFinalizable::trace(Visitor* visitor)
 {
     visitor->trace(m_onHeap);
 }
@@ skipping 10 matching lines @@
     MixinFinalizable::trace(visitor);
 }
 
 void NeedsNoFinalization::trace(Visitor* visitor)
 {
     visitor->trace(m_obj);
     MixinNotFinalizable::trace(visitor);
 }
 
 }