Let IPC::SyncMessageFilter take advantage of thread-safe Send.

ppapi/nacl_irt/manifest_service.h

Index: ppapi/nacl_irt/manifest_service.h
diff --git a/ppapi/nacl_irt/manifest_service.h b/ppapi/nacl_irt/manifest_service.h
index 7a869e7c58a8bde1c0d1909b84ab14d01ed6887c..4a648d9bda1ff302d1beb8cb8e6c20ac0cdb3fdb 100644
--- a/ppapi/nacl_irt/manifest_service.h
+++ b/ppapi/nacl_irt/manifest_service.h
@@ -17,7 +17,7 @@ class WaitableEvent;
 
 namespace IPC {
 struct ChannelHandle;
-class ChannelProxy;
+class SyncChannel;
 class SyncMessageFilter;
 }  // namespace IPC
 
@@ -34,7 +34,7 @@ class ManifestService {
   bool OpenResource(const char* file, int* fd);
 
  private:
-  scoped_ptr<IPC::ChannelProxy> channel_;
+  scoped_ptr<IPC::SyncChannel> channel_;
   scoped_refptr<IPC::SyncMessageFilter> filter_;
 
   base::Lock open_resource_lock_;