Add an end-to-end test that excercises Mojo with a sandbox.

content/shell/utility/mojo_test_impl.cc

+// 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.
+
+#include "content/shell/utility/mojo_test_impl.h"
+
+#include <utility>
+
+#include "mojo/public/cpp/system/buffer.h"
+
+namespace content {
+
+// static
+void MojoTestImpl::CreateMojoTestImpl(
+    mojo::InterfaceRequest<mojom::MojoTest> request) {
+  new MojoTestImpl(std::move(request));
+}
+
+MojoTestImpl::MojoTestImpl(mojo::InterfaceRequest<mojom::MojoTest> request)
+  : binding_(this, std::move(request)) {}
+
+MojoTestImpl::~MojoTestImpl() {}
+
+void MojoTestImpl::MakeSharedBuffer(uint32_t size,
+                                    const MakeSharedBufferCallback& callback) {
+  mojo::ScopedSharedBufferHandle handle;
+  MojoResult result = mojo::CreateSharedBuffer(nullptr, size, &handle);
+  LOG(INFO) << "mojo::CreateSharedBuffer result: " << result;
+  callback.Run(std::move(handle));
+}
+
+
+}  // namespace content