Move more files into the content namespace.

content/browser/renderer_host/render_widget_host_impl.h

Index: content/browser/renderer_host/render_widget_host_impl.h
===================================================================
--- content/browser/renderer_host/render_widget_host_impl.h	(revision 147462)
+++ content/browser/renderer_host/render_widget_host_impl.h	(working copy)
@@ -24,7 +24,6 @@
 #include "ui/base/ime/text_input_type.h"
 #include "ui/gfx/native_widget_types.h"
 
-class BackingStore;
 class MockRenderWidgetHost;
 class WebCursor;
 struct EditCommand;
@@ -46,7 +45,7 @@
 }
 
 namespace content {
-
+class BackingStore;
 class RenderWidgetHostDelegate;
 class RenderWidgetHostViewPort;
 class SmoothScrollGesture;