bluetooth: Add device list retrieval for chrome://bluetooth-internals

device/bluetooth/public/interfaces/adapter.mojom

+// 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.
+
+module bluetooth.mojom;
+
+struct DeviceInfo {
+  string? name;
+  string name_for_display;
+  string id;
+  string address;
+};
+
+interface Adapter {
+  // Retrieves the list of the devices known by the adapter including Connected
+  // Devices, GATT Connected Devices, Paired Devices and Devices discovered
+  // during a classic or low-energy scan.
+  GetDevices() => (array<DeviceInfo> devices);
+
+  // Sets the client that listens for the adapter's events.

[dpapad, 2016/10/03 17:51:03]

Optional: It is not clear at all that the "client" is the WebUI page here. Can
we use the same terminology as plugins.mojom, meaning setClientPage()?. See
https://cs.chromium.org/chromium/src/chrome/browser/ui/webui/plugins/plugins.....

Also I suggest changing the "Adapter" generic names as follows

Adapter -> BluetoothPageHandler
AdapterClient -> BluetoothPage

I think this makes it much clearer (self-documenting) who is the C++ handler,
who is the WebUI page.

[mbrunson, 2016/10/03 18:56:03]

This Mojo interface will not be used exclusively by the WebUI. The plan is for
it to become part of a set of interfaces that all developers will use to
communicate with device/bluetooth. That's why it's named this way.

+  SetClient(AdapterClient client);
+};
+
+interface AdapterClient {
+  // Called the first time a device is discovered.
+  DeviceAdded(DeviceInfo device);
+
+  // Called after the device hasn't been seen for 3 minutes.
+  DeviceRemoved(DeviceInfo device);
+};