Move Render(View|Widget)Host and associated classes to content namespace.

content/browser/renderer_host/render_widget_host_view_mac.mm

Index: content/browser/renderer_host/render_widget_host_view_mac.mm
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.mm b/content/browser/renderer_host/render_widget_host_view_mac.mm
index e7bc839db2510f84ca35d3c579c4e4720fcbe122..2f1e2da5485de593650aef85fd2549cb5893dea9 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/content/browser/renderer_host/render_widget_host_view_mac.mm
@@ -50,6 +50,9 @@
 #include "webkit/plugins/npapi/webplugin.h"
 
 using content::BrowserThread;
+using content::RenderViewHostImpl;
+using content::RenderWidgetHost;
+using content::RenderWidgetHostImpl;
 using content::RenderWidgetHostView;
 using WebKit::WebInputEvent;
 using WebKit::WebInputEventFactory;