Revert of arc: Use the new InstanceHolder for unittests

components/arc/test/fake_app_instance.h

Index: components/arc/test/fake_app_instance.h
diff --git a/components/arc/test/fake_app_instance.h b/components/arc/test/fake_app_instance.h
index fd5b6d6f772cb487d3668fdb4d99ec95708d8552..e3b220cd34ea1fc2b8b2f5a0a1e74e2a6e707da3 100644
--- a/components/arc/test/fake_app_instance.h
+++ b/components/arc/test/fake_app_instance.h
@@ -79,6 +79,10 @@
   explicit FakeAppInstance(mojom::AppHost* app_host);
   ~FakeAppInstance() override;
 
+  void Bind(mojo::InterfaceRequest<mojom::AppInstance> interface_request) {
+    binding_.Bind(std::move(interface_request));
+  }
+
   // mojom::AppInstance overrides:
   void Init(mojom::AppHostPtr host_ptr) override {}
   void RefreshAppList() override;
@@ -148,9 +152,24 @@
     return shortcut_icon_requests_;
   }
 
+  // This method can be called on tests when a method is intended to
+  // be called across a Mojo proxy.
+  void WaitForIncomingMethodCall();
+
+  // As part of the initialization process, the instance side calls
+  // mojom::AppHost::OnAppInstanceReady(), which in turn calls
+  // mojom::AppInstance::Init() and
+  // mojom::AppInstance::RefreshAppList(). This method should be called after a
+  // call
+  // to mojom::ArcBridgeHost::OnAppInstanceReady() to make sure all method calls
+  // have
+  // been dispatched.
+  void WaitForOnAppInstanceReady();
+
  private:
   using TaskIdToInfo = std::map<int32_t, std::unique_ptr<Request>>;
   // Mojo endpoints.
+  mojo::Binding<mojom::AppInstance> binding_;
   mojom::AppHost* app_host_;
   // Number of RefreshAppList calls.
   int refresh_app_list_count_ = 0;