Modify the default brightness of the screen

修改屏幕默认亮度值：MTKSettingsProvider\res\values\defaults.xml
<integer name="def_screen_brightness">255</integer>  生效

修改屏幕默认亮度值：frameworks/base/core/res/res/values/config.xml
<integer name="config_screenBrightnessSettingDefault">255</integer> 不生效

    /**
    *屏幕亮度控制类
    */
      // The default screen brightness.
    private final int mScreenBrightnessDefault;

   public DisplayPowerController(Context context,
            DisplayPowerCallbacks callbacks, Handler handler,
            SensorManager sensorManager, DisplayBlanker blanker) {
        mHandler = new DisplayControllerHandler(handler.getLooper());
        mBrightnessTracker = new BrightnessTracker(context, null);
        mSettingsObserver = new SettingsObserver(mHandler);
        mCallbacks = callbacks;

        mBatteryStats = BatteryStatsService.getService();
        mSensorManager = sensorManager;
        mWin