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..d7ceecdb0eeecdae0e34ff687592b0219c80a597 100644
--- a/device/bluetooth/bluez/bluetooth_device_bluez.cc
+++ b/device/bluetooth/bluez/bluetooth_device_bluez.cc
@@ -11,6 +11,7 @@
 
 #include "base/bind.h"
 #include "base/metrics/histogram.h"
+#include "base/optional.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "dbus/bus.h"
@@ -137,6 +138,11 @@ BluetoothDevice::ConnectErrorCode DBusErrorToConnectError(
   return error_code;
 }
 
+base::Optional<int8_t> EnsureValidPower(int16_t power) {
+  return ((power < INT8_MIN) || (power > INT8_MAX)) ? base::Optional<int8_t>()
+                                                    : power;
+}
+
 }  // namespace
 
 namespace bluez {
@@ -316,28 +322,28 @@ BluetoothDeviceBlueZ::UUIDList BluetoothDeviceBlueZ::GetUUIDs() const {
   return uuids;
 }
 
-int16_t BluetoothDeviceBlueZ::GetInquiryRSSI() const {
+base::Optional<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 base::Optional<int8_t>();
 
-  return properties->rssi.value();
+  return EnsureValidPower(properties->rssi.value());
 }
 
-int16_t BluetoothDeviceBlueZ::GetInquiryTxPower() const {
+base::Optional<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 base::Optional<int8_t>();
 
-  return properties->tx_power.value();
+  return EnsureValidPower(properties->tx_power.value());
 }
 
 bool BluetoothDeviceBlueZ::ExpectingPinCode() const {
@@ -594,11 +600,20 @@ void BluetoothDeviceBlueZ::GattServiceRemoved(
   adapter()->NotifyGattServiceRemoved(service);
 }
 
-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));
+void BluetoothDeviceBlueZ::OnGetConnInfo(
+    const ConnectionInfoCallback& callback,
+    const base::Optional<int16_t>& rssi,
+    const base::Optional<int16_t>& transmit_power,
+    const base::Optional<int16_t>& max_transmit_power) {
+  if (!rssi) {
+    DCHECK(!transmit_power);
+    DCHECK(!max_transmit_power);
+    callback.Run(ConnectionInfo());
+  }
+
+  callback.Run(ConnectionInfo(EnsureValidPower(rssi.value()),
+                              EnsureValidPower(transmit_power.value()),
+                              EnsureValidPower(max_transmit_power.value())));
 }
 
 void BluetoothDeviceBlueZ::OnGetConnInfoError(