Remove DeferBackgroundExtensionCreation field trial and supporting code

chrome/browser/ui/startup/startup_browser_creator_impl.cc

 // Copyright (c) 2012 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/ui/startup/startup_browser_creator_impl.h"
 
 #include <algorithm>
 #include <vector>
 
 #include "apps/app_restore_service.h"
@@ skipping 400 matching lines @@
       KeystoneInfoBar::PromotionInfoBar(profile);
     }
 #endif
   }
 
 #if defined(OS_WIN)
   if (process_startup)
     ShellIntegration::MigrateChromiumShortcuts();
 #endif  // defined(OS_WIN)
 
-#if defined(ENABLE_EXTENSIONS)
-  // If we deferred creation of background extension hosts, we want to create
-  // them now that the session (if any) has been restored.
-  extensions::ProcessManager* process_manager =
-      extensions::ExtensionSystem::Get(profile)->process_manager();
-  process_manager->DeferBackgroundHostCreation(false);
-#endif
-
   return true;
 }
 
 void StartupBrowserCreatorImpl::ExtractOptionalAppWindowSize(
     gfx::Rect* bounds) {
   if (command_line_.HasSwitch(switches::kAppWindowSize)) {
     int width, height;
     width = height = 0;
     std::string switch_value =
         command_line_.GetSwitchValueASCII(switches::kAppWindowSize);
@@ skipping 552 matching lines @@
 }
 
 #if !defined(OS_WIN)
 // static
 bool StartupBrowserCreatorImpl::OpenStartupURLsInExistingBrowser(
     Profile* profile,
     const std::vector<GURL>& startup_urls) {
   return false;
 }
 #endif