bluetooth: Add FakeBluetooth interface

device/bluetooth/README.md

 # Bluetooth
 
 `device/bluetooth` abstracts
 [Bluetooth Classic](https://en.wikipedia.org/wiki/Bluetooth) and
 [Low Energy](https://en.wikipedia.org/wiki/Bluetooth_low_energy) features
 across multiple platforms.
 
 Classic and Low Energy based profiles differ substantially. Platform
 implementations may support only one or the other, even though several classes
 have interfaces for both, e.g. `BluetoothAdapter` & `BluetoothDevice`.
@@ skipping 31 matching lines @@
 
 Known future work is tracked in the
 [Refactoring meta issue](https://crbug.com/580406).
 
 
 ## Testing
 
 Implementation of the Bluetooth component is tested via unittests. Client code
 uses Mock Bluetooth objects:
 
+### Mojo Testing Interface
+A Mojo Testing Interface is defined at
+`src/device/bluetooth/public/interfaces/test/fake_bluetooth.mojom`.
+Clients can use this interface to control a fake implementation of the non-mojo
+C++ Bluetooth interface. The implementation of this test interface lives at
+`src/device/bluetooth/test/`. *This interface will be removed once a Bluetooth

[scheib, 2017/04/10 21:52:31]

'will be removed' is hard to say... ;) 'should' or 'may' is better. Perhaps
explain why: 

"""
This interface may be removed when a Bluetooth Mojo Service is introduced.
Testing code would implement the service as needed for tests.
"""

However, I also wonder how likely this is. This interface is a reusable test
interface that is likely to be pretty convenient to use. If multiple clients
need to test, it would save them effort vs each one creating a fake mojo service
impl, right?

[ortuno, 2017/04/12 05:49:06]

Done. I added that we'll remove it if Web Bluetooth is the only client.
I think it will depend on the approach we take when we add the Bluetooth
service. But based on the push back against refactoring clients to use the mojo
service directly and insistence on just using the current interface (T_T) my
guess is that we won't need this.

+Mojo Service is introduced.*
 
 ### Cross Platform Unit Tests
 
 New feature development uses cross platform unit tests. This reduces test code
 redundancy and produces consistency across all implementations.
 
 Unit tests operate at the public `device/bluetooth` API layer and the
 `BluetoothTest` fixture controls fake operating system behavior as close to the
 platfom as possible. The resulting test coverage spans the cross platform API,
 common implementation, and platform specific implementation as close to
@@ skipping 25 matching lines @@
 
 ### Chrome OS Blueooth Controller Tests
 
 Bluetooth controller system tests generating radio signals are run and managed
 by the Chrome OS team. See:
 https://chromium.googlesource.com/chromiumos/third_party/autotest/+/master/server/site_tests/
 https://chromium.googlesource.com/chromiumos/third_party/autotest/+/master/server/cros/bluetooth/
 https://chromium.googlesource.com/chromiumos/third_party/autotest/+/master/client/cros/bluetooth/
 
 
 ## Android

[scheib, 2017/04/12 18:56:46]

I don't think this Android heading should be moved. It primarily is discussing
the architecture of the C++/Java objects and ownership. It also explains how
testing is done -- but that's more of a sub-point of the overall "Hey, Android
is weird because C++/Java". The testing bits could stay here (what I'd do), or
be edited out and migrated to the test directory.

[ortuno, 2017/04/13 01:12:47]

Done.

 
 The android implementation requires crossing from C++ to Java using
 [__JNI__](https://www.chromium.org/developers/design-documents/android-jni).
 
 Object ownership is rooted in the C++ classes, starting with the Adapter, which
 owns Devices, Services, etc. Java counter parts interface with the Android
 Bluetooth objects. E.g.
 
 For testing, the Android objects are __wrapped__ in:
 `android/java/src/org/chromium/device/bluetooth/Wrappers.java`. <br>
@@ skipping 21 matching lines @@
 See also: [Class Diagram of Web Bluetooth through Bluetooth Android][Class]
 
 [Class]: https://sites.google.com/a/chromium.org/dev/developers/design-documents/bluetooth-design-docs/web-bluetooth-through-bluetooth-android-class-diagram
 
 
 ## Design Documents
 
 * [Bluetooth Notifications](https://docs.google.com/document/d/1guBtAnQUP8ZoZre4VQGrjR5uX0ZYxfK-lwKNeqY0-z4/edit?usp=sharing) 2016-08-26
     * Web Bluetooth through Android implementation details, class diagram and
       call flow.