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

components/html_viewer/content_handler_impl.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_HTML_VIEWER_CONTENT_HANDLER_IMPL_H_
 #define COMPONENTS_HTML_VIEWER_CONTENT_HANDLER_IMPL_H_
 
 #include "base/macros.h"
 #include "mojo/application/public/cpp/application_impl.h"
 #include "mojo/application/public/interfaces/content_handler.mojom.h"
 #include "third_party/mojo/src/mojo/public/cpp/bindings/strong_binding.h"
 
 namespace html_viewer {
 
 class GlobalState;
 
 class ContentHandlerImpl : public mojo::ContentHandler {
  public:
   ContentHandlerImpl(GlobalState* global_state,
                      mojo::ApplicationImpl* app,
                      mojo::InterfaceRequest<ContentHandler> request);
   ~ContentHandlerImpl() override;
 
  protected:
   GlobalState* global_state() const { return global_state_; }
   mojo::ApplicationImpl* app() const { return app_; }
 
  private:
   // Overridden from 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;
 
   GlobalState* global_state_;
   mojo::ApplicationImpl* app_;
   mojo::StrongBinding<mojo::ContentHandler> binding_;
+  scoped_ptr<mojo::AppRefCount> app_refcount_;
 
   DISALLOW_COPY_AND_ASSIGN(ContentHandlerImpl);
 };
 
 }  // namespace html_viewer
 
 #endif  // COMPONENTS_HTML_VIEWER_CONTENT_HANDLER_IMPL_H_