Move content's a plugin, ppapi_plugin, utility, and worker subdirectories to the content namespace.

content/plugin/webplugin_accelerated_surface_proxy_mac.h

Index: content/plugin/webplugin_accelerated_surface_proxy_mac.h
===================================================================
--- content/plugin/webplugin_accelerated_surface_proxy_mac.h	(revision 163080)
+++ content/plugin/webplugin_accelerated_surface_proxy_mac.h	(working copy)
@@ -9,9 +9,11 @@
 #include "ui/gl/gpu_preference.h"
 #include "webkit/plugins/npapi/webplugin_accelerated_surface_mac.h"
 
-class WebPluginProxy;
 class AcceleratedSurface;
 
+namespace content {
+class WebPluginProxy;
+
 // Out-of-process implementation of WebPluginAcceleratedSurface that proxies
 // calls through a WebPluginProxy.
 class WebPluginAcceleratedSurfaceProxy
@@ -47,4 +49,6 @@
   DISALLOW_COPY_AND_ASSIGN(WebPluginAcceleratedSurfaceProxy);
 };
 
+}  // namespace content
+
 #endif  // CONTENT_PLUGIN_WEBPLUGIN_ACCELERATED_SURFACE_PROXY_H_