Clean up remaining uses of WebCore namespace

Source/core/dom/DOMRect.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 "config.h"
 #include "core/dom/DOMRect.h"
 
-namespace WebCore {
+namespace blink {
 
 DOMRect* DOMRect::create(double x, double y, double width, double height)
 {
     return new DOMRect(x, y, width, height);
 }
 
 DOMRect::DOMRect(double x, double y, double width, double height)
     : DOMRectReadOnly(x, y, width, height)
 {
 }
 
-} // namespace WebCore
+} // namespace blink