Extract LazyBackgroundTaskQueue from ExtensionSystem.

extensions/browser/api/runtime/runtime_api.cc

Index: extensions/browser/api/runtime/runtime_api.cc
diff --git a/extensions/browser/api/runtime/runtime_api.cc b/extensions/browser/api/runtime/runtime_api.cc
index cc90d3732c2e5824609fc4a5bcd590550cc02628..09ed7d99b0e35a6e1e9498be5c678496762a9a6d 100644
--- a/extensions/browser/api/runtime/runtime_api.cc
+++ b/extensions/browser/api/runtime/runtime_api.cc
@@ -95,9 +95,9 @@ void DispatchOnStartupEventImpl(BrowserContext* browser_context,
           extension_id);
   if (extension && BackgroundInfo::HasPersistentBackgroundPage(extension) &&
       first_call &&
-      system->lazy_background_task_queue()->ShouldEnqueueTask(browser_context,
-                                                              extension)) {
-    system->lazy_background_task_queue()->AddPendingTask(
+      LazyBackgroundTaskQueue::Get(browser_context)->ShouldEnqueueTask(
+          browser_context, extension)) {
+    LazyBackgroundTaskQueue::Get(browser_context)->AddPendingTask(
         browser_context,
         extension_id,
         base::Bind(
@@ -404,12 +404,11 @@ void RuntimeEventRouter::OnExtensionUninstalled(
 }
 
 ExtensionFunction::ResponseAction RuntimeGetBackgroundPageFunction::Run() {
-  ExtensionSystem* system = ExtensionSystem::Get(browser_context());
   ExtensionHost* host = ProcessManager::Get(browser_context())
                             ->GetBackgroundHostForExtension(extension_id());
-  if (system->lazy_background_task_queue()->ShouldEnqueueTask(browser_context(),
-                                                              extension())) {
-    system->lazy_background_task_queue()->AddPendingTask(
+  if (LazyBackgroundTaskQueue::Get(browser_context())->ShouldEnqueueTask(
+          browser_context(), extension())) {
+    LazyBackgroundTaskQueue::Get(browser_context())->AddPendingTask(
         browser_context(),
         extension_id(),
         base::Bind(&RuntimeGetBackgroundPageFunction::OnPageLoaded, this));