Allow EmbedRoot to be called multiple times.

mojo/services/public/cpp/view_manager/window_manager_delegate.h

+// Copyright 2014 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_SERVICES_PUBLIC_CPP_VIEW_MANAGER_WINDOW_MANAGER_DELEGATE_H_
+#define MOJO_SERVICES_PUBLIC_CPP_VIEW_MANAGER_WINDOW_MANAGER_DELEGATE_H_
+
+#include "mojo/services/public/interfaces/input_events/input_events.mojom.h"
+
+namespace mojo {
+namespace view_manager {
+
+class View;
+
+// A WindowManagerDelegate is provided by the application embedded at the
+// service root node.
+class WindowManagerDelegate {
+ public:
+  // Create an appropriate node to embed |url|.
+  virtual void EmbedRoot(const String& url) = 0;
+
+  // Dispatch the supplied input event to the appropriate view (taking into
+  // account focus, activation, modality, etc.).
+  virtual void DispatchEvent(View* target, EventPtr event) = 0;
+
+ protected:
+  virtual ~WindowManagerDelegate() {}
+};
+
+}  // namespace view_manager
+}  // namespace mojo
+
+#endif  // MOJO_SERVICES_PUBLIC_CPP_VIEW_MANAGER_WINDOW_MANAGER_DELEGATE_H_