Add a Mojo example apptest that runs in mojo_shell.

mojo/examples/apptest/example_client_impl.h

Index: mojo/examples/apptest/example_client_impl.h
diff --git a/mojo/examples/apptest/example_client_impl.h b/mojo/examples/apptest/example_client_impl.h
new file mode 100644
index 0000000000000000000000000000000000000000..739778c375764fe309601e8b9e9a72ec567aef25
--- /dev/null
+++ b/mojo/examples/apptest/example_client_impl.h
@@ -0,0 +1,32 @@
+// 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_EXAMPLES_TEST_EXAMPLE_CLIENT_IMPL_H_
+#define MOJO_EXAMPLES_TEST_EXAMPLE_CLIENT_IMPL_H_
+
+#include "mojo/examples/apptest/example_service.mojom.h"
+#include "mojo/public/cpp/system/macros.h"
+
+namespace mojo {
+
+class ApplicationConnection;
+
+class ExampleClientImpl : public InterfaceImpl<ExampleClient> {
+ public:
+  explicit ExampleClientImpl();
+  virtual ~ExampleClientImpl();
+
+  int16_t last_pong_value() const { return last_pong_value_; }
+
+ private:
+  // InterfaceImpl<ExampleClient> overrides.
+  virtual void Pong(uint16_t pong_value) MOJO_OVERRIDE;
+
+  int16_t last_pong_value_;
+  MOJO_DISALLOW_COPY_AND_ASSIGN(ExampleClientImpl);
+};
+
+}  // namespace mojo
+
+#endif  // MOJO_EXAMPLES_TEST_EXAMPLE_CLIENT_IMPL_H_