Add visibility control for the UiBlocker

The existing UiBlocker mechanism doesn't support additional visibility
control. With that, controllers that want to control their own
visibility won't be able to use UiBlocker.

Fixes: 223340393
Test: robotest
Change-Id: I2df2eb1ce77e2c94bb271a8b68cc8c6004df5c70

src/com/android/settings/dashboard/UiBlockerController.java

@@ -37,7 +37,7 @@ import java.util.concurrent.TimeUnit;
  */
 public class UiBlockerController {
     private static final String TAG = "UiBlockerController";
-    private static final int TIMEOUT_MILLIS = 500;
+    private static final int TIMEOUT_MILLIS = 300;
 
     private CountDownLatch mCountDownLatch;
     private boolean mBlockerFinished;