bluetooth: Return int8_t and use -128 for unknown tx power.

device/bluetooth/bluez/bluetooth_device_bluez.cc

Index: device/bluetooth/bluez/bluetooth_device_bluez.cc
diff --git a/device/bluetooth/bluez/bluetooth_device_bluez.cc b/device/bluetooth/bluez/bluetooth_device_bluez.cc
index 73e54871143c0599a4789e551dcd622dbde82343..4a14f6156328271882191e344ba9a2da6d67aeec 100644
--- a/device/bluetooth/bluez/bluetooth_device_bluez.cc
+++ b/device/bluetooth/bluez/bluetooth_device_bluez.cc
@@ -137,6 +137,16 @@ BluetoothDevice::ConnectErrorCode DBusErrorToConnectError(
   return error_code;
 }
 
+int8_t EnsureValidRSSI(int16_t rssi) {
+  return ((rssi < -128) || (rssi > 127)) ? BluetoothDevice::kUnknownRSSI : rssi;
+}
+
+int8_t EnsureValidTxPower(int16_t tx_power) {
+  return ((tx_power < -127) || (tx_power > 127))
+             ? BluetoothDevice::kUnknownTxPower
+             : tx_power;
+}
+
 }  // namespace
 
 namespace bluez {
@@ -316,28 +326,28 @@ BluetoothDeviceBlueZ::UUIDList BluetoothDeviceBlueZ::GetUUIDs() const {
   return uuids;
 }
 
-int16_t BluetoothDeviceBlueZ::GetInquiryRSSI() const {
+int8_t BluetoothDeviceBlueZ::GetInquiryRSSI() const {
   bluez::BluetoothDeviceClient::Properties* properties =
       bluez::BluezDBusManager::Get()->GetBluetoothDeviceClient()->GetProperties(
           object_path_);
   DCHECK(properties);
 
   if (!properties->rssi.is_valid())
-    return kUnknownPower;
+    return kUnknownRSSI;
 
-  return properties->rssi.value();
+  return EnsureValidRSSI(properties->rssi.value());
 }
 
-int16_t BluetoothDeviceBlueZ::GetInquiryTxPower() const {
+int8_t BluetoothDeviceBlueZ::GetInquiryTxPower() const {
   bluez::BluetoothDeviceClient::Properties* properties =
       bluez::BluezDBusManager::Get()->GetBluetoothDeviceClient()->GetProperties(
           object_path_);
   DCHECK(properties);
 
   if (!properties->tx_power.is_valid())
-    return kUnknownPower;
+    return kUnknownTxPower;
 
-  return properties->tx_power.value();
+  return EnsureValidTxPower(properties->tx_power.value());
 }
 
 bool BluetoothDeviceBlueZ::ExpectingPinCode() const {
@@ -598,7 +608,9 @@ void BluetoothDeviceBlueZ::OnGetConnInfo(const ConnectionInfoCallback& callback,
                                          int16_t rssi,
                                          int16_t transmit_power,
                                          int16_t max_transmit_power) {
-  callback.Run(ConnectionInfo(rssi, transmit_power, max_transmit_power));
+  callback.Run(ConnectionInfo(EnsureValidRSSI(rssi),
+                              EnsureValidTxPower(transmit_power),
+                              EnsureValidTxPower(max_transmit_power)));
 }
 
 void BluetoothDeviceBlueZ::OnGetConnInfoError(