[extensions] Fix use-after-free in ExtensionAlarmsTest

1. Fix the destruction order in extensions_tests;
2. Declare the explicit dependency: AlarmManager => ExtensionRegistry.

Change-Id: Ibe734d3b39ba9a0d3dfae7c233c82c77336ec4bd
Reviewed-on: https://chromium-review.googlesource.com/964144Reviewed-by: Ken Rockot <rockot@chromium.org>
Commit-Queue: Mikhail Atuchin <atuchin@yandex-team.ru>
Cr-Commit-Position: refs/heads/master@{#543772}

extensions/browser/api/alarms/alarm_manager.cc

@@ -20,6 +20,7 @@
 #include "extensions/browser/api/alarms/alarms_api_constants.h"
 #include "extensions/browser/event_router.h"
 #include "extensions/browser/extension_registry.h"
+#include "extensions/browser/extension_registry_factory.h"
 #include "extensions/browser/extension_system.h"
 #include "extensions/browser/state_store.h"
 #include "extensions/common/api/alarms.h"
@@ -231,6 +232,11 @@ static base::LazyInstance<
     BrowserContextKeyedAPIFactory<AlarmManager>>::DestructorAtExit g_factory =
     LAZY_INSTANCE_INITIALIZER;
 
+template <>
+void BrowserContextKeyedAPIFactory<AlarmManager>::DeclareFactoryDependencies() {
+  DependsOn(ExtensionRegistryFactory::GetInstance());
+}
+
 // static
 BrowserContextKeyedAPIFactory<AlarmManager>*
 AlarmManager::GetFactoryInstance() {

extensions/browser/extensions_test.cc

@@ -108,16 +108,16 @@ void ExtensionsTest::TearDown() {
   // Allows individual tests to have BrowserContextKeyedServiceFactory objects
   // as member variables instead of singletons. The individual services will be
   // cleaned up before the factories are destroyed.
-  BrowserContextDependencyManager::GetInstance()->DestroyBrowserContextServices(
-      browser_context_.get());
   BrowserContextDependencyManager::GetInstance()->DestroyBrowserContextServices(
       incognito_context_.get());
+  BrowserContextDependencyManager::GetInstance()->DestroyBrowserContextServices(
+      browser_context_.get());
 
   extensions_browser_client_.reset();
   ExtensionsBrowserClient::Set(nullptr);
 
-  browser_context_.reset();
   incognito_context_.reset();
+  browser_context_.reset();
   pref_service_.reset();
 }