Clean up remaining uses of WebCore namespace

Source/core/dom/DOMRect.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 DOMRect_h
 #define DOMRect_h
 
 #include "bindings/core/v8/Dictionary.h"
 #include "core/dom/DOMRectReadOnly.h"
 
-namespace WebCore {
+namespace blink {
 
 class DOMRect FINAL : public DOMRectReadOnly {
 public:
     static DOMRect* create(double x = 0, double y = 0, double width = 0, double height = 0);
 
     void setX(double x) { m_x = x; }
     void setY(double y) { m_y = y; }
     void setWidth(double width) { m_width = width; }
     void setHeight(double height) { m_height = height; }
 
 protected:
     DOMRect(double x, double y, double z, double w);
 };
 
-} // namespace WebCore
+} // namespace blink
 
 #endif