Add helpers for creating UI components.

mojo/ui/input_handler.h

Index: mojo/ui/input_handler.h
diff --git a/mojo/ui/input_handler.h b/mojo/ui/input_handler.h
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+// 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 MOJO_UI_INPUT_HANDLER_H_
+#define MOJO_UI_INPUT_HANDLER_H_
+
+#include "mojo/public/cpp/bindings/binding.h"
+#include "mojo/public/cpp/system/macros.h"
+#include "mojo/public/interfaces/application/service_provider.mojom.h"
+#include "mojo/services/ui/input/interfaces/input_connection.mojom.h"
+
+namespace mojo {
+namespace ui {
+
+// Holds an |InputConnection| and sets its |InputListener|.
+//
+// This class is intended to be included as a member of a View that wants to
+// receive input using the following pattern.
+//
+// class MyView : public mojo::ui::BaseView, public mojo::ui::InputListener {
+//  public:
+//   MyView(mojo::ApplicationImpl* app_impl,
+//          const mojo::ui::ViewProvider::CreateViewCallback&
+//              create_view_callback)
+//          : BaseView(app_impl, "MyView", create_view_callback),
+//            input_handler_(view_service_provider(), this) {}
+//   ~MyView() override {}
+//
+//  private:
+//   // |InputListener|:
+//   void OnEvent(mojo::EventPtr event,
+//                const OnEventCallback& callback) override;
+//
+//   mojo::ui::InputHandler input_handler_;
+//
+//   MOJO_DISALLOW_COPY_AND_ASSIGN(MyView);
+// };
+class InputHandler {
+ public:
+  // Creates an input connection associated with the specified view host.
+  InputHandler(mojo::ServiceProvider* service_provider,
+               mojo::ui::InputListener* listener);
+  ~InputHandler();
+
+  // Gets the input connection.
+  mojo::ui::InputConnection* connection() { return connection_.get(); }
+
+ private:
+  mojo::Binding<mojo::ui::InputListener> listener_binding_;
+  mojo::ui::InputConnectionPtr connection_;
+
+  MOJO_DISALLOW_COPY_AND_ASSIGN(InputHandler);
+};
+
+}  // namespace ui
+}  // namespace mojo
+
+#endif  // MOJO_UI_INPUT_HANDLER_H_