Ensure we don't load plugins on the IO thread

webkit/tools/test_shell/test_shell_mac.mm

 // Copyright (c) 2006-2008 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 <ApplicationServices/ApplicationServices.h>
 #import <Cocoa/Cocoa.h>
 #import <objc/objc-runtime.h>
 #include <sys/stat.h>
 
 #include "webkit/tools/test_shell/test_shell.h"
@@ skipping 682 matching lines @@
   case IDR_SEARCH_MAGNIFIER_RESULTS:
     return TestShell::NetResourceProvider(resource_id);
 
   default:
     break;
   }
 
   return StringPiece();
 }
 
-bool GetPlugins(bool refresh, std::vector<WebPluginInfo>* plugins) {
-  return NPAPI::PluginList::Singleton()->GetPlugins(refresh, plugins);
+void GetPlugins(bool refresh, std::vector<WebPluginInfo>* plugins) {
+  NPAPI::PluginList::Singleton()->GetPlugins(refresh, plugins);
 }
 
 bool DownloadUrl(const std::string& url, NSWindow* caller_window) {
   return false;
 }
 
 void DidLoadPlugin(const std::string& filename) {
 }
 
 void DidUnloadPlugin(const std::string& filename) {
 }
 
 }  // namespace webkit_glue