Expose TxPower for bluetooth devices during discovery

device/bluetooth/bluetooth_device.h

Index: device/bluetooth/bluetooth_device.h
diff --git a/device/bluetooth/bluetooth_device.h b/device/bluetooth/bluetooth_device.h
index d4e7d426f04a37497c28e6ec4e374300ee1bbd7c..ccf71dadfd2cadd13ee57be4ee5289d07c03f3ae 100644
--- a/device/bluetooth/bluetooth_device.h
+++ b/device/bluetooth/bluetooth_device.h
@@ -263,6 +263,12 @@ class DEVICE_BLUETOOTH_EXPORT BluetoothDevice {
   // this method will return |kUnknownPower|.
   virtual int16 GetInquiryRSSI() const = 0;
 
+  // The transmitted power level. This field is avaliable only for LE devices
+  // that include this field in AD. It is avaliable and valid only during
+  // discovery. If not during discovery, or TxPower wasn't reported, this
+  // method will return |kUnknownPower|.
+  virtual int16 GetInquiryTxPower() const = 0;
+
   // The ErrorCallback is used for methods that can fail in which case it
   // is called, in the success case the callback is simply not called.
   typedef base::Callback<void()> ErrorCallback;