Convert more interfaces to the new thunk system.

ppapi/proxy/ppb_file_system_proxy.h

Index: ppapi/proxy/ppb_file_system_proxy.h
===================================================================
--- ppapi/proxy/ppb_file_system_proxy.h	(revision 87260)
+++ ppapi/proxy/ppb_file_system_proxy.h	(working copy)
@@ -8,6 +8,7 @@
 #include <string>
 
 #include "base/basictypes.h"
+#include "ppapi/c/dev/ppb_file_system_dev.h"
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_resource.h"
 #include "ppapi/c/pp_time.h"
@@ -29,9 +30,8 @@
 
   static const Info* GetInfo();
 
-  const PPB_FileSystem_Dev* ppb_file_system_target() const {
-    return static_cast<const PPB_FileSystem_Dev*>(target_interface());
-  }
+  static PP_Resource CreateProxyResource(PP_Instance instance,
+                                         PP_FileSystemType_Dev type);
 
   // InterfaceProxy implementation.
   virtual bool OnMessageReceived(const IPC::Message& msg);