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

tools/clang/blink_gc_plugin/tests/base_requires_tracing.h

 // 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.
 
 #ifndef BASE_REQUIRES_TRACING_H_
 #define BASE_REQUIRES_TRACING_H_
 
 #include "heap/stubs.h"
 
-namespace WebCore {
+namespace blink {
 
 class A : public GarbageCollected<A> {
 public:
     virtual void trace(Visitor*);
 };
 
 class B : public A {
     // Does not need trace
 };
 
 class C : public B {
 public:
     void trace(Visitor*);
 private:
     Member<A> m_a;
 };
 
 class D : public C {
 public:
     void trace(Visitor*);
 private:
     Member<A> m_a;
 };
 
 }
 
 #endif