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

content/plugin/webplugin_accelerated_surface_proxy_mac.cc

Index: content/plugin/webplugin_accelerated_surface_proxy_mac.cc
===================================================================
--- content/plugin/webplugin_accelerated_surface_proxy_mac.cc	(revision 163080)
+++ content/plugin/webplugin_accelerated_surface_proxy_mac.cc	(working copy)
@@ -14,6 +14,8 @@
 #include "ui/surface/io_surface_support_mac.h"
 #include "ui/surface/transport_dib.h"
 
+namespace content {
+
 WebPluginAcceleratedSurfaceProxy* WebPluginAcceleratedSurfaceProxy::Create(
     WebPluginProxy* plugin_proxy,
     gfx::GpuPreference gpu_preference) {
@@ -119,3 +121,5 @@
         window_handle_, surface_->GetSurfaceId());
   }
 }
+
+}  // namespace content