bluetooth: mac: add connected LE devices to chooser

device/bluetooth/bluetooth_low_energy_discovery_manager_mac.mm

Index: device/bluetooth/bluetooth_low_energy_discovery_manager_mac.mm
diff --git a/device/bluetooth/bluetooth_low_energy_discovery_manager_mac.mm b/device/bluetooth/bluetooth_low_energy_discovery_manager_mac.mm
index eeb1ace3beb1996e17dc2abb39103a7ffc787899..70cece66244dc5197c4c2f70b60d6d532e31148c 100644
--- a/device/bluetooth/bluetooth_low_energy_discovery_manager_mac.mm
+++ b/device/bluetooth/bluetooth_low_energy_discovery_manager_mac.mm
@@ -73,6 +73,21 @@ void BluetoothLowEnergyDiscoveryManagerMac::TryStartDiscovery() {
                                CBCentralManagerScanOptionAllowDuplicatesKey :
                                    @YES
                              }];
+  NSArray* connectedServices;
+  if (services) {
+    connectedServices = services;
+  } else {
+    CBUUID* defaultService = [CBUUID UUIDWithString:@"1800"];

[François Beaufort, 2016/09/15 07:38:16]

You may want to add a comment there to explain why we've picked "Generic Access"
service UUID:
https://www.bluetooth.com/specifications/gatt/viewer?attributeXmlFile=org.blu...

In the future, we should consider adding previously connected devices as well. 

[jlebel, 2016/09/21 13:49:28]

Done.

+    connectedServices = @[ defaultService ];
+  }
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wpartial-availability"

[François Beaufort, 2016/09/15 07:38:16]

According to
https://developer.apple.com/reference/corebluetooth/cbcentralmanager/1518924-...,
retrieveConnectedPeripheralsWithServices has been introduced in macOS 10.9.
Shouldn't we update src/base/mac/sdk_forward_declarations.h?

[jlebel, 2016/09/21 13:49:28]

I think it is a terrible idea to create a fake declaration to avoid a compiler
warning. I prefer to be explicit: ask the compiler to not generate the warning.

+  NSArray* peripherals = [central_manager_
+      retrieveConnectedPeripheralsWithServices:connectedServices];
+#pragma clang diagnostic pop
+  for (CBPeripheral* peripheral in peripherals) {
+    observer_->LowEnergyDeviceUpdated(peripheral, nil, 0);

[François Beaufort, 2016/09/15 07:38:16]

Nit:  observer_->LowEnergyDeviceUpdated(peripheral, nil /* advertisementData */,
0 /* rssi */);

[jlebel, 2016/09/21 13:49:28]

Done.

+  }
   pending_ = false;
 }