Convert //ash from scoped_ptr to std::unique_ptr

ash/test/ash_test_base.h

Index: ash/test/ash_test_base.h
diff --git a/ash/test/ash_test_base.h b/ash/test/ash_test_base.h
index c8aa7365044bf99d70c1ecada6db906d8ec79ccd..21f0fc5460560584cbe6fc4b5c88c568bd55325d 100644
--- a/ash/test/ash_test_base.h
+++ b/ash/test/ash_test_base.h
@@ -148,9 +148,9 @@ class AshTestBase : public testing::Test {
   bool teardown_called_;
   // |SetUp()| doesn't activate session if this is set to false.
   bool start_session_;
-  scoped_ptr<content::TestBrowserThreadBundle> thread_bundle_;
-  scoped_ptr<AshTestHelper> ash_test_helper_;
-  scoped_ptr<ui::test::EventGenerator> event_generator_;
+  std::unique_ptr<content::TestBrowserThreadBundle> thread_bundle_;
+  std::unique_ptr<AshTestHelper> ash_test_helper_;
+  std::unique_ptr<ui::test::EventGenerator> event_generator_;
 #if defined(OS_WIN)
   ui::ScopedOleInitializer ole_initializer_;
 #endif