Add support for mapping node tree on the client.

mojo/services/public/cpp/view_manager/lib/view_manager_observer.h

Index: mojo/services/public/cpp/view_manager/lib/view_manager_observer.h
diff --git a/mojo/services/public/cpp/view_manager/lib/view_manager_observer.h b/mojo/services/public/cpp/view_manager/lib/view_manager_observer.h
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index 0000000000000000000000000000000000000000..4a9d44cda559087e10d0ba84837fb10378ac6d82
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+++ b/mojo/services/public/cpp/view_manager/lib/view_manager_observer.h
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+// 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_LIB_VIEW_MANAGER_OBSERVER_H_
+#define MOJO_SERVICES_PUBLIC_CPP_VIEW_MANAGER_LIB_VIEW_MANAGER_OBSERVER_H_
+
+namespace mojo {
+namespace services {
+namespace view_manager {
+
+class ViewManagerObserver {
+ public:
+  // Called when the client establishes a connection with the service.
+  virtual void OnViewManagerConnected(ViewManager* manager) = 0;
+
+  // Called when a commit is made to the service.
+  virtual void OnCommit(ViewManager* manager) = 0;
+
+  // Called when a response was received to a prior commit.
+  virtual void OnCommitResponse(ViewManager* manager, bool success) = 0;
+
+ protected:
+  virtual ~ViewManagerObserver() {}
+};
+
+}  // namespace view_manager
+}  // namespace services
+}  // namespace mojo
+
+#endif  // MOJO_SERVICES_PUBLIC_CPP_VIEW_MANAGER_LIB_VIEW_MANAGER_OBSERVER_H_