Reland of arc: Use the new InstanceHolder for unittests

components/arc/test/fake_notifications_instance.h

Index: components/arc/test/fake_notifications_instance.h
diff --git a/components/arc/test/fake_notifications_instance.h b/components/arc/test/fake_notifications_instance.h
index c1c1e39448f3059141bcf87ec7f2bc368c23362f..1cc91802cf67064d46469ca5243ced0e5b937e32 100644
--- a/components/arc/test/fake_notifications_instance.h
+++ b/components/arc/test/fake_notifications_instance.h
@@ -15,8 +15,7 @@ namespace arc {
 
 class FakeNotificationsInstance : public mojom::NotificationsInstance {
  public:
-  FakeNotificationsInstance(
-      mojo::InterfaceRequest<mojom::NotificationsInstance> request);
+  FakeNotificationsInstance();
   ~FakeNotificationsInstance() override;
 
   void Init(mojom::NotificationsHostPtr host_ptr) override;
@@ -28,13 +27,9 @@ class FakeNotificationsInstance : public mojom::NotificationsInstance {
   const std::vector<std::pair<mojo::String, mojom::ArcNotificationEvent>>&
   events() const;
 
-  void WaitForIncomingMethodCall();
-
  private:
   std::vector<std::pair<mojo::String, mojom::ArcNotificationEvent>> events_;
 
-  mojo::Binding<mojom::NotificationsInstance> binding_;
-
   DISALLOW_COPY_AND_ASSIGN(FakeNotificationsInstance);
 };