Refactor code that defers extension background page loading

extensions/browser/test_extensions_browser_client.cc

Index: extensions/browser/test_extensions_browser_client.cc
diff --git a/extensions/browser/test_extensions_browser_client.cc b/extensions/browser/test_extensions_browser_client.cc
index dcd467f3ceea91f2db9e85e5e9f50d91ac44a310..383929397f3562bbbdb83de432ae62ea1b3e7ff6 100644
--- a/extensions/browser/test_extensions_browser_client.cc
+++ b/extensions/browser/test_extensions_browser_client.cc
@@ -15,7 +15,9 @@ namespace extensions {
 
 TestExtensionsBrowserClient::TestExtensionsBrowserClient(
     BrowserContext* main_context)
-    : main_context_(main_context), incognito_context_(NULL) {
+    : main_context_(main_context),
+      incognito_context_(NULL),
+      defer_loading_background_hosts_(false) {
   DCHECK(main_context_);
   DCHECK(!main_context_->IsOffTheRecord());
 }
@@ -118,7 +120,7 @@ void TestExtensionsBrowserClient::GetEarlyExtensionPrefsObservers(
 
 bool TestExtensionsBrowserClient::DeferLoadingBackgroundHosts(
     BrowserContext* context) const {
-  return false;
+  return defer_loading_background_hosts_;
 }
 
 bool TestExtensionsBrowserClient::IsBackgroundPageAllowed(
@@ -148,9 +150,8 @@ ApiActivityMonitor* TestExtensionsBrowserClient::GetApiActivityMonitor(
 
 ExtensionSystemProvider*
 TestExtensionsBrowserClient::GetExtensionSystemFactory() {
-  // Tests requiring an extension system should override this function.
-  NOTREACHED();
-  return NULL;
+  DCHECK(extension_system_factory_);
+  return extension_system_factory_;
 }
 
 void TestExtensionsBrowserClient::RegisterExtensionFunctions(