PPAPI: Force async callback invocation option.

ppapi/example/example.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <math.h>
 #include <stdio.h>  // FIXME(brettw) erase me.
 #ifndef _WIN32
 #include <sys/time.h>
 #else
 #include <windows.h>
@@ skipping 89 matching lines @@
              const pp::Var& url,
              MyFetcherClient* client) {
     pp::URLRequestInfo request;
     request.SetURL(url);
     request.SetMethod("GET");
 
     loader_ = pp::URLLoader(instance);
     client_ = client;
 
     pp::CompletionCallback callback =
-        callback_factory_.NewCallback(&MyFetcher::DidOpen);
+        callback_factory_.NewOptionalCallback(&MyFetcher::DidOpen);
     int rv = loader_.Open(request, callback);
     if (rv != PP_OK_COMPLETIONPENDING)
       callback.Run(rv);
   }
 
   void StartWithOpenedLoader(const pp::URLLoader& loader,
                              MyFetcherClient* client) {
     loader_ = loader;
     client_ = client;
 
     ReadMore();
   }
 
  private:
   void ReadMore() {
     pp::CompletionCallback callback =
-        callback_factory_.NewCallback(&MyFetcher::DidRead);
+        callback_factory_.NewOptionalCallback(&MyFetcher::DidRead);
     int rv = loader_.ReadResponseBody(buf_, sizeof(buf_), callback);
     if (rv != PP_OK_COMPLETIONPENDING)
       callback.Run(rv);
   }
 
   void DidOpen(int32_t result) {
     if (result == PP_OK) {
       ReadMore();
     } else {
       DidFinish(result);
@@ skipping 344 matching lines @@
 };
 
 namespace pp {
 
 // Factory function for your specialization of the Module object.
 Module* CreateModule() {
   return new MyModule();
 }
 
 }  // namespace pp