Convert the PluginResource to be refcounted.

ppapi/proxy/ppb_buffer_proxy.cc

Index: ppapi/proxy/ppb_buffer_proxy.cc
diff --git a/ppapi/proxy/ppb_buffer_proxy.cc b/ppapi/proxy/ppb_buffer_proxy.cc
index 19442ea98a6fccf0d08ddfcdd32dc671fc375ff8..57dba6ca6f3ffbcad6ef9ee6f1f7a6c76ae1bffe 100644
--- a/ppapi/proxy/ppb_buffer_proxy.cc
+++ b/ppapi/proxy/ppb_buffer_proxy.cc
@@ -116,8 +116,8 @@ PP_Resource PPB_Buffer_Proxy::AddProxyResource(
     const HostResource& resource,
     base::SharedMemoryHandle shm_handle,
     uint32_t size) {
-  linked_ptr<Buffer> object(new Buffer(resource, shm_handle, size));
-  return PluginResourceTracker::GetInstance()->AddResource(object);
+  return PluginResourceTracker::GetInstance()->AddResource(
+      new Buffer(resource, shm_handle, size));
 }
 
 bool PPB_Buffer_Proxy::OnMessageReceived(const IPC::Message& msg) {