Reseting scrollposition to 0 when going to keyguard

This avoids some jank when going to the keyguard from
the locked shade.

Change-Id: I21dcd8a7cbb2aa98659061d29670b2663f1e7fc9

packages/SystemUI/src/com/android/systemui/statusbar/phone/NotificationPanelView.java

@@ -482,6 +482,7 @@ public class NotificationPanelView extends PanelView implements
         mStatusBar.dismissPopups();
         mNotificationStackScroller.setOverScrollAmount(0f, true /* onTop */, false /* animate */,
                 true /* cancelAnimators */);
+        mNotificationStackScroller.resetScrollPosition();
     }
 
     public void closeQs() {

packages/SystemUI/src/com/android/systemui/statusbar/stack/NotificationStackScrollLayout.java

@@ -2230,6 +2230,11 @@ public class NotificationStackScrollLayout extends ViewGroup
         }
     }
 
+    public void resetScrollPosition() {
+        mScroller.abortAnimation();
+        mOwnScrollY = 0;
+    }
+
     private void setIsExpanded(boolean isExpanded) {
         boolean changed = isExpanded != mIsExpanded;
         mIsExpanded = isExpanded;