Revert "Delete the ViewManager and WindowManager services."

mojo/services/view_manager/cpp/lib/view_observer.cc

Index: mojo/services/view_manager/cpp/lib/view_observer.cc
diff --git a/mojo/services/view_manager/cpp/lib/view_observer.cc b/mojo/services/view_manager/cpp/lib/view_observer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..a72b51474373f838903b2d4fc03cd53cd3c96986
--- /dev/null
+++ b/mojo/services/view_manager/cpp/lib/view_observer.cc
@@ -0,0 +1,18 @@
+// 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.
+
+#include "view_manager/cpp/view_observer.h"
+
+namespace mojo {
+
+////////////////////////////////////////////////////////////////////////////////
+// ViewObserver, public:
+
+ViewObserver::TreeChangeParams::TreeChangeParams()
+    : target(nullptr),
+      old_parent(nullptr),
+      new_parent(nullptr),
+      receiver(nullptr) {}
+
+}  // namespace mojo