Fix hangs in Mandoline page cycler on Linux with --enable-multiprocess.

components/html_viewer/layout_test_content_handler_impl.h

Index: components/html_viewer/layout_test_content_handler_impl.h
diff --git a/components/html_viewer/layout_test_content_handler_impl.h b/components/html_viewer/layout_test_content_handler_impl.h
index 0113783fed8bc74cc4751ed8c558a090ee536fc2..5dc9cac411a57704504eed05ba9493b4632accf5 100644
--- a/components/html_viewer/layout_test_content_handler_impl.h
+++ b/components/html_viewer/layout_test_content_handler_impl.h
@@ -37,8 +37,10 @@ class LayoutTestContentHandlerImpl : public ContentHandlerImpl,
                                 HTMLWidgetRootLocal::CreateParams*>;
 
   // ContentHandler:
-  void StartApplication(mojo::InterfaceRequest<mojo::Application> request,
-                        mojo::URLResponsePtr response) override;
+  void StartApplication(
+      mojo::InterfaceRequest<mojo::Application> request,
+      mojo::URLResponsePtr response,
+      const mojo::Callback<void()>& destruct_callback) override;
 
   // HTMLFactory
   HTMLFrame* CreateHTMLFrame(HTMLFrame::CreateParams* params) override;
@@ -48,6 +50,7 @@ class LayoutTestContentHandlerImpl : public ContentHandlerImpl,
   test_runner::WebTestInterfaces* test_interfaces_;
   WebTestDelegateImpl* test_delegate_;
   WebWidgetProxy* web_widget_proxy_;
+  scoped_ptr<mojo::AppRefCount> app_refcount_;
 
   DISALLOW_COPY_AND_ASSIGN(LayoutTestContentHandlerImpl);
 };