chrome.bluetoothLowEnergy: Implement writeDescriptorValue.

chrome/browser/extensions/api/bluetooth_low_energy/bluetooth_low_energy_api.h

Index: chrome/browser/extensions/api/bluetooth_low_energy/bluetooth_low_energy_api.h
diff --git a/chrome/browser/extensions/api/bluetooth_low_energy/bluetooth_low_energy_api.h b/chrome/browser/extensions/api/bluetooth_low_energy/bluetooth_low_energy_api.h
index f817adbc7a0808838ea622e919244245388b69d4..f455b9aed0ba4105199aa40f88e03fa2cfd5a32b 100644
--- a/chrome/browser/extensions/api/bluetooth_low_energy/bluetooth_low_energy_api.h
+++ b/chrome/browser/extensions/api/bluetooth_low_energy/bluetooth_low_energy_api.h
@@ -241,6 +241,15 @@ class BluetoothLowEnergyWriteDescriptorValueFunction
 
   // BluetoothLowEnergyExtensionFunction override.
   virtual bool DoWork() OVERRIDE;
+
+ private:
+  // Success and error callbacks, called by
+  // BluetoothLowEnergyEventRouter::WriteDescriptorValue.
+  void SuccessCallback();
+  void ErrorCallback();
+
+  // The instance ID of the requested descriptor.
+  std::string instance_id_;
 };
 
 }  // namespace api