Creates mus test helper class

components/mus/public/cpp/tests/window_tree_client_impl_private.h

Index: components/mus/public/cpp/tests/window_tree_client_impl_private.h
diff --git a/components/mus/public/cpp/tests/window_tree_client_impl_private.h b/components/mus/public/cpp/tests/window_tree_client_impl_private.h
new file mode 100644
index 0000000000000000000000000000000000000000..c1544aee444eca2c6df6d534fd2e1609ce133cbe
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+++ b/components/mus/public/cpp/tests/window_tree_client_impl_private.h
@@ -0,0 +1,38 @@
+// Copyright 2016 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 COMPONENTS_MUS_PUBLIC_CPP_TESTS_WINDOW_TREE_CLIENT_IMPL_PRIVATE_H_
+#define COMPONENTS_MUS_PUBLIC_CPP_TESTS_WINDOW_TREE_CLIENT_IMPL_PRIVATE_H_
+
+#include <stdint.h>
+
+#include "base/macros.h"
+
+namespace mus {
+namespace mojom {
+class WindowTree;
+}
+
+class WindowTreeClientImpl;
+
+// Use to access implementation details of WindowTreeClientImpl.
+class WindowTreeClientImplPrivate {
+ public:
+  explicit WindowTreeClientImplPrivate(WindowTreeClientImpl* tree_client_impl);
+  ~WindowTreeClientImplPrivate();
+
+  uint32_t event_observer_id();
+
+  // Calls OnEmbed() on the WindowTreeClientImpl.
+  void OnEmbed(mojom::WindowTree* window_tree);
+
+ private:
+  WindowTreeClientImpl* tree_client_impl_;
+
+  DISALLOW_COPY_AND_ASSIGN(WindowTreeClientImplPrivate);
+};
+
+}  // namespace mus
+
+#endif  // COMPONENTS_MUS_PUBLIC_CPP_TESTS_WINDOW_TREE_CLIENT_IMPL_PRIVATE_H_