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

content/plugin/webplugin_delegate_stub.h

Index: content/plugin/webplugin_delegate_stub.h
===================================================================
--- content/plugin/webplugin_delegate_stub.h	(revision 163080)
+++ content/plugin/webplugin_delegate_stub.h	(working copy)
@@ -17,8 +17,6 @@
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/rect.h"
 
-class PluginChannel;
-class WebPluginProxy;
 struct PluginMsg_Init_Params;
 struct PluginMsg_DidReceiveResponseParams;
 struct PluginMsg_UpdateGeometry_Param;
@@ -34,6 +32,10 @@
 }
 }
 
+namespace content {
+class PluginChannel;
+class WebPluginProxy;
+
 // Converts the IPC messages from WebPluginDelegateProxy into calls to the
 // actual WebPluginDelegateImpl object.
 class WebPluginDelegateStub : public IPC::Listener,
@@ -134,4 +136,6 @@
   DISALLOW_IMPLICIT_CONSTRUCTORS(WebPluginDelegateStub);
 };
 
+}  // namespace content
+
 #endif  // CONTENT_PLUGIN_WEBPLUGIN_DELEGATE_STUB_H_