Use PluginPrefs in ChromePluginServiceFilter to check whether a plugin is enabled.

chrome/browser/browser_process_impl.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 "chrome/browser/browser_process_impl.h"
 
 #include <map>
 #include <set>
 #include <vector>
 
 #include "base/command_line.h"
 #include "base/file_util.h"
 #include "base/path_service.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/task.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_restrictions.h"
 #include "chrome/browser/automation/automation_provider_list.h"
 #include "chrome/browser/background/background_mode_manager.h"
 #include "chrome/browser/browser_main.h"
 #include "chrome/browser/browser_process_sub_thread.h"
 #include "chrome/browser/browser_trial.h"
+#include "chrome/browser/chrome_plugin_service_filter.h"
 #include "chrome/browser/component_updater/component_updater_configurator.h"
 #include "chrome/browser/component_updater/component_updater_service.h"
 #include "chrome/browser/debugger/devtools_protocol_handler.h"
 #include "chrome/browser/debugger/remote_debugging_server.h"
 #include "chrome/browser/download/download_file_manager.h"
 #include "chrome/browser/extensions/extension_event_router_forwarder.h"
 #include "chrome/browser/extensions/extension_tab_id_map.h"
 #include "chrome/browser/extensions/user_script_listener.h"
 #include "chrome/browser/first_run/upgrade_util.h"
 #include "chrome/browser/google/google_url_tracker.h"
@@ skipping 694 matching lines @@
 }
 
 void BrowserProcessImpl::CreateIOThread() {
   DCHECK(!created_io_thread_ && io_thread_.get() == NULL);
   created_io_thread_ = true;
 
   // Prior to starting the io thread, we create the plugin service as
   // it is predominantly used from the io thread, but must be created
   // on the main thread. The service ctor is inexpensive and does not
   // invoke the io_thread() accessor.
-  PluginService::GetInstance();
+  PluginService::GetInstance()->set_filter(
+      ChromePluginServiceFilter::GetInstance());
 
   // Add the Chrome specific plugins.
   chrome::RegisterInternalDefaultPlugin();
 
   // Register the internal Flash if available.
   FilePath path;
   if (!CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kDisableInternalFlash) &&
       PathService::Get(chrome::FILE_FLASH_PLUGIN, &path)) {
     webkit::npapi::PluginList::Singleton()->AddExtraPluginPath(path);
@@ skipping 370 matching lines @@
 }
 
 void BrowserProcessImpl::OnAutoupdateTimer() {
   if (CanAutorestartForUpdate()) {
     DLOG(WARNING) << "Detected update.  Restarting browser.";
     RestartPersistentInstance();
   }
 }
 
 #endif  // (defined(OS_WIN) || defined(OS_LINUX)) && !defined(OS_CHROMEOS)