Fix jump cut when dismissing items in Recents

(fixing horizontal scroll view in this CL... whoops).

Bug: 7070897
Change-Id: I3a63799ce7f3d9a50869755ee3289e641fa82fa4

Author: mikejurka

packages/SystemUI/src/com/android/systemui/recent/RecentsHorizontalScrollView.java

@@ -156,19 +156,19 @@ public boolean onLongClick(View v) {
         }
         setLayoutTransition(transitioner);
 
-        // Scroll to end after layout.
-        final ViewTreeObserver observer = getViewTreeObserver();
+        // Scroll to end after initial layout.
 
         final OnGlobalLayoutListener updateScroll = new OnGlobalLayoutListener() {
                 public void onGlobalLayout() {
                     mLastScrollPosition = scrollPositionOfMostRecent();
                     scrollTo(mLastScrollPosition, 0);
+                    final ViewTreeObserver observer = getViewTreeObserver();
                     if (observer.isAlive()) {
                         observer.removeOnGlobalLayoutListener(this);
                     }
                 }
             };
-        observer.addOnGlobalLayoutListener(updateScroll);
+        getViewTreeObserver().addOnGlobalLayoutListener(updateScroll);
     }
 
     @Override