bluetooth: Change GetInquiryTxPower and GetInquiryRSSI to return optional.

device/bluetooth/bluetooth_device.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef DEVICE_BLUETOOTH_BLUETOOTH_DEVICE_H_
 #define DEVICE_BLUETOOTH_BLUETOOTH_DEVICE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 287 matching lines @@
   //  * For connected Low Energy Devices for which services have been discovered
   //    returns the UUIDs of the device's services.
   //  * For dual mode devices this may be collected from both.
   //
   // Note: On ChromeOS and Linux, Bluez persists all services meaning if
   // a device stops advertising a service this function will still return
   // its UUID.
   virtual UUIDList GetUUIDs() const;
 
   // The received signal strength, in dBm. This field is avaliable and valid
-  // only during discovery. If not during discovery, or RSSI wasn't reported,
-  // this method will return |kUnknownPower|.
-  virtual int16_t GetInquiryRSSI() const = 0;
+  // only during discovery.
+  virtual base::Optional<int8_t> 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_t GetInquiryTxPower() const = 0;
+  // discovery.
+  virtual base::Optional<int8_t> 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;
 
   // The ConnectErrorCallback is used for methods that can fail with an error,
   // passed back as an error code argument to this callback.
   // In the success case this callback is not called.
   typedef base::Callback<void(enum ConnectErrorCode)> ConnectErrorCallback;
 
@@ skipping 267 matching lines @@
 
  private:
   // Returns a localized string containing the device's bluetooth address and
   // a device type for display when |name_| is empty.
   base::string16 GetAddressWithLocalizedDeviceTypeName() const;
 };
 
 }  // namespace device
 
 #endif  // DEVICE_BLUETOOTH_BLUETOOTH_DEVICE_H_