Extract LazyBackgroundTaskQueue from ExtensionSystem.

extensions/shell/browser/shell_extension_system.cc

Index: extensions/shell/browser/shell_extension_system.cc
diff --git a/extensions/shell/browser/shell_extension_system.cc b/extensions/shell/browser/shell_extension_system.cc
index b4512df220794e5a3529fdebf31f6dd1e2c9d6ca..e5cabb7321867c419e7756af3a334eacf3bd2644 100644
--- a/extensions/shell/browser/shell_extension_system.cc
+++ b/extensions/shell/browser/shell_extension_system.cc
@@ -18,7 +18,6 @@
 #include "extensions/browser/extension_prefs.h"
 #include "extensions/browser/extension_registry.h"
 #include "extensions/browser/info_map.h"
-#include "extensions/browser/lazy_background_task_queue.h"
 #include "extensions/browser/notification_types.h"
 #include "extensions/browser/quota_service.h"
 #include "extensions/browser/runtime_data.h"
@@ -98,8 +97,6 @@ void ShellExtensionSystem::Shutdown() {
 void ShellExtensionSystem::InitForRegularProfile(bool extensions_enabled) {
   runtime_data_.reset(
       new RuntimeData(ExtensionRegistry::Get(browser_context_)));
-  lazy_background_task_queue_.reset(
-      new LazyBackgroundTaskQueue(browser_context_));
   event_router_.reset(
       new EventRouter(browser_context_, ExtensionPrefs::Get(browser_context_)));
   quota_service_.reset(new QuotaService);
@@ -135,10 +132,6 @@ InfoMap* ShellExtensionSystem::info_map() {
   return info_map_.get();
 }
 
-LazyBackgroundTaskQueue* ShellExtensionSystem::lazy_background_task_queue() {
-  return lazy_background_task_queue_.get();
-}
-
 EventRouter* ShellExtensionSystem::event_router() {
   return event_router_.get();
 }