Dim the screen quickly in response to user activity timeout.

Reverts a previous change that made the screen dim slowly instead.
The quick transition does a better job of attracting the user's
attention to the fact that the screen is about to turn off
unless the user touches the screen.

Bug: 7386034
Change-Id: I81e4d8939f6791b96352004984a9e5b2aab79788

Author: Jeff Brown

services/java/com/android/server/power/DisplayPowerController.java

@@ -648,10 +648,10 @@ private void updatePowerState() {
                 mUsingScreenAutoBrightness = false;
             }
             if (mPowerRequest.screenState == DisplayPowerRequest.SCREEN_STATE_DIM) {
-                // Dim slowly by at least some minimum amount.
+                // Dim quickly by at least some minimum amount.
                 target = Math.min(target - SCREEN_DIM_MINIMUM_REDUCTION,
                         mScreenBrightnessDimConfig);
-                slow = true;
+                slow = false;
             } else if (wasDim) {
                 // Brighten quickly.
                 slow = false;