SystemUI: Hide notifications when quickly expanding QS

Expand/collapse animation with the 2 finger swipe/swipe down from
right side to expand QS gesture [1] was pretty ugly with all the
notifications being dragged along. Let's hide the notifications
stack entirely when quickly expanding QS, for a nicer looking
animation similar to the one in lockscreen.

[1]: pa-gr/android_frameworks_base@d362239

Change-Id: Id2dbc707f9da543d47d76ae5525e827b400a4e7b

Author: adithya2306

packages/SystemUI/src/com/android/systemui/shade/NotificationPanelViewController.java

@@ -3339,6 +3339,9 @@ private void updateNotificationTranslucency() {
                 && !mKeyguardBypassController.getBypassEnabled()) {
             alpha *= mClockPositionResult.clockAlpha;
         }
+        if (mQsExpandImmediate && !mQsFullyExpanded) {
+            alpha = 0f;
+        }
         mNotificationStackScrollLayoutController.setAlpha(alpha);
         if (mBarState != StatusBarState.KEYGUARD && !isFullyCollapsed() && !isPanelVisibleBecauseOfHeadsUp()) {
             mCentralSurfaces.updateDismissAllVisibility(true);