mandoline: Add back/forward support and UI.

mandoline/ui/phone_ui/phone_browser_application_delegate.cc

 // 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.
 
 #include "mandoline/ui/phone_ui/phone_browser_application_delegate.h"
 
 #include "base/command_line.h"
 #include "components/view_manager/public/cpp/view.h"
 #include "components/view_manager/public/cpp/view_tree_connection.h"
 #include "components/view_manager/public/cpp/view_tree_host_factory.h"
@@ skipping 97 matching lines @@
 }
 
 void PhoneBrowserApplicationDelegate::LoadingStateChanged(bool is_loading) {
   // ...
 }
 
 void PhoneBrowserApplicationDelegate::ProgressChanged(double progress) {
   // ...
 }
 
+
+void PhoneBrowserApplicationDelegate::BackForwardChanged(
+    web_view::mojom::ButtonState back_button,
+    web_view::mojom::ButtonState forward_button) {
+  // ...
+}
+
 void PhoneBrowserApplicationDelegate::TitleChanged(const mojo::String& title) {
   // ...
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // PhoneBrowserApplicationDelegate,
 //       mojo::InterfaceFactory<LaunchHandler> implementation:
 
 void PhoneBrowserApplicationDelegate::Create(
     mojo::ApplicationConnection* connection,
     mojo::InterfaceRequest<LaunchHandler> request) {
   launch_handler_bindings_.AddBinding(this, request.Pass());
 }
 
 }  // namespace mandoline