Remove DeferBackgroundExtensionCreation field trial and supporting code

chrome/browser/extensions/extension_system.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/extensions/extension_system.h"
 
 #include "base/base_switches.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
@@ skipping 319 matching lines @@
   }
 }
 
 ExtensionSystemImpl::~ExtensionSystemImpl() {
 }
 
 void ExtensionSystemImpl::Shutdown() {
   process_manager_.reset();
 }
 
-void ExtensionSystemImpl::InitForRegularProfile(
-    bool extensions_enabled,
-    bool defer_background_creation) {
+void ExtensionSystemImpl::InitForRegularProfile(bool extensions_enabled) {
   DCHECK(!profile_->IsOffTheRecord());
   if (user_script_master() || extension_service())
     return;  // Already initialized.
 
   // The InfoMap needs to be created before the ProcessManager.
   shared_->info_map();
 
   process_manager_.reset(ProcessManager::Create(profile_));
 
-  process_manager_->DeferBackgroundHostCreation(
-      defer_background_creation);
-
   shared_->Init(extensions_enabled);
 }
 
 ExtensionService* ExtensionSystemImpl::extension_service() {
   return shared_->extension_service();
 }
 
 ManagementPolicy* ExtensionSystemImpl::management_policy() {
   return shared_->management_policy();
 }
@@ skipping 76 matching lines @@
 void ExtensionSystemImpl::UnregisterExtensionWithRequestContexts(
     const std::string& extension_id,
     const UnloadedExtensionInfo::Reason reason) {
   BrowserThread::PostTask(
       BrowserThread::IO,
       FROM_HERE,
       base::Bind(&InfoMap::RemoveExtension, info_map(), extension_id, reason));
 }
 
 }  // namespace extensions