bluetooth: Implement RSSI and Tx Power on macOS and Android

device/bluetooth/bluetooth_adapter_mac.mm

Index: device/bluetooth/bluetooth_adapter_mac.mm
diff --git a/device/bluetooth/bluetooth_adapter_mac.mm b/device/bluetooth/bluetooth_adapter_mac.mm
index ef4a20dee2da1156e992a84add68576b47755754..2e25aab0800c1030a4ff20b2e6cba73e159e91b9 100644
--- a/device/bluetooth/bluetooth_adapter_mac.mm
+++ b/device/bluetooth/bluetooth_adapter_mac.mm
@@ -539,8 +539,18 @@ void BluetoothAdapterMac::LowEnergyDeviceUpdated(
                              std::vector<uint8_t>(bytes, bytes + length));
   }
 
-  device_mac->UpdateAdvertisementData(std::move(advertised_uuids),
-                                      std::move(service_data_map));
+  // Get Tx Power.
+  NSNumber* tx_power =
+      [advertisement_data objectForKey:CBAdvertisementDataTxPowerLevelKey];
+  base::Optional<int8_t> clamped_tx_power =
+      tx_power == nil ? base::nullopt
+                      : base::make_optional<int8_t>(
+                            BluetoothDevice::ClampPower([tx_power intValue]));

[Jeffrey Yasskin, 2016/08/24 22:32:07]

Same reminder here as on Android. I forget about the details of ObjC, but it's
possible that [tx_power intValue] will return some default when tx_power is nil,
and then you could just write "int8_t clamped_tx_power =
BluetoothDevice::ClampPower([tx_power intValue])"

[ortuno, 2016/08/25 16:42:34]

Done. [tx_power intValue] is 0 when tx_power is nil.

+
+  device_mac->UpdateAdvertisementData(
+      BluetoothDevice::ClampPower(rssi), std::move(advertised_uuids),
+      std::move(service_data_map),
+      clamped_tx_power ? &clamped_tx_power.value() : nullptr);
 
   if (is_new_device) {
     std::string device_address =