Move LazyBackgroundTaskQueueTest into extensions_unittests

extensions/browser/test_extensions_browser_client.h

Index: extensions/browser/test_extensions_browser_client.h
diff --git a/extensions/browser/test_extensions_browser_client.h b/extensions/browser/test_extensions_browser_client.h
index 5933e195a5a35934cc94f7f8d4b73d1b2a2a792d..7e77050abc224c8edf46728844dbd733d7b4dae5 100644
--- a/extensions/browser/test_extensions_browser_client.h
+++ b/extensions/browser/test_extensions_browser_client.h
@@ -22,6 +22,9 @@ class TestExtensionsBrowserClient : public ExtensionsBrowserClient {
   void set_process_manager_delegate(ProcessManagerDelegate* delegate) {
     process_manager_delegate_ = delegate;
   }
+  void set_extension_system_factory(ExtensionSystemProvider* factory) {

[Yoyo Zhou, 2014/08/01 22:13:10]

It seems slightly odd to set the factory rather than the system. Guess it's a
byproduct of ExtensionSystem::Get.

[James Cook, 2014/08/01 22:48:03]

Yeah, this is awkward. I don't remember why ExtensionSystemProvider was built
this way. I'm guessing it's because an ExtensionSystemProvider subclass has to
express the ExtensionSystemFactory DependsOn() calls?

I wish ExtensionsBrowserClient just had a GetExtensionSystem() method. Should I
investigate that possibility for another CL?

[Yoyo Zhou, 2014/08/01 23:00:30]

Yes, I think it was for the dependencies on other factories. If you want to look
into it, feel free to, but don't spend too much time on it, I suppose. =)

+    extension_system_factory_ = factory;
+  }
 
   // Associates an incognito context with |main_context_|.
   void SetIncognitoContext(content::BrowserContext* incognito_context);
@@ -88,6 +91,9 @@ class TestExtensionsBrowserClient : public ExtensionsBrowserClient {
   // Not owned, defaults to NULL.
   ProcessManagerDelegate* process_manager_delegate_;
 
+  // Not owned, defaults to NULL.
+  ExtensionSystemProvider* extension_system_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(TestExtensionsBrowserClient);
 };