Move more files into the content namespace.

content/browser/renderer_host/backing_store.cc

 // Copyright (c) 2010 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 "content/browser/renderer_host/backing_store.h"
 
-BackingStore::BackingStore(content::RenderWidgetHost* widget,
-                           const gfx::Size& size)
+namespace content {
+
+BackingStore::BackingStore(RenderWidgetHost* widget, const gfx::Size& size)
     : render_widget_host_(widget),
       size_(size) {
 }
 
 BackingStore::~BackingStore() {
 }
 
 size_t BackingStore::MemorySize() {
   return size_.GetArea() * 4;
 }
+
+}  // namespace content