bluetooth: Add Device connection logic and accompanying user interface.

device/bluetooth/test/device_connection_helper.h

Index: device/bluetooth/test/device_connection_helper.h
diff --git a/device/bluetooth/test/device_connection_helper.h b/device/bluetooth/test/device_connection_helper.h
new file mode 100644
index 0000000000000000000000000000000000000000..7b02b6814d9581cce2ecb7ed12ab0826f77bb114
--- /dev/null
+++ b/device/bluetooth/test/device_connection_helper.h
@@ -0,0 +1,37 @@
+// 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 DEVICE_BLUETOOTH_DEVICE_CONNECTION_HELPER_H_
+#define DEVICE_BLUETOOTH_DEVICE_CONNECTION_HELPER_H_
+
+#include "device/bluetooth/public/interfaces/device.mojom.h"
+#include "mojo/public/cpp/bindings/binding.h"
+
+namespace bluetooth {
+
+// Helper class to verify the order of destruction of callbacks and Mojo message
+// pipe. DeviceConnectionHelper is owned by the callback, and DCHECKs when
+// the owning callback is destroyed before the message pipe is closed.

[dcheng, 2016/11/11 01:25:33]

The test code is pretty complex, and part of that ends up bleeding over into
non-test code. Can you help me understand why it's necessary to verify these
sorts of things? What sort of problems does this test aim to catch?

[mbrunson, 2016/11/11 21:26:15]

It's mainly to test whether the callbacks for a Device.GetServices request are
deleted before the Device's message pipe is closed.

+class DeviceConnectionHelper {
+ public:
+  DeviceConnectionHelper(mojo::Binding<mojom::Device>* binding);

[dcheng, 2016/11/11 01:25:33]

Nit: explicit

[mbrunson, 2016/11/11 21:26:15]

Done.

+  ~DeviceConnectionHelper();
+
+  // Sets the callback ran flag. If callback ran flag is set to true, no check
+  // is performed when this instance is detroyed.
+  void SetCallbackRan(bool callback_ran);
+
+ private:
+  // Flag that marks when a callback has been run.
+  bool callback_ran_;
+
+  // Device binding that holds the message pipe that's checked on destruction.
+  mojo::Binding<mojom::Device>* binding_;
+
+  DISALLOW_COPY_AND_ASSIGN(DeviceConnectionHelper);
+};
+
+}  // namespace bluetooth
+
+#endif  // DEVICE_BLUETOOTH_DEVICE_CONNECTION_HELPER_H_