Simplifying fast scroller logic

> Using a separate view for drawing the popup. This allows us to use elevation
  property instead of drawing the shadow as bitmap.
> During the thumb animation, invalidating the full track width, instead of
  invalidating the track and thumb separately.
> The thumb path is calculated at 0,0 and drawn using canvas.translate().
   This avoids recalculating the path on every scroll.

Change-Id: I48741e5b4432df0d939016db284d7aaf52cc2aa6

src/com/android/launcher3/allapps/AllAppsContainerView.java

@@ -272,7 +272,7 @@ public class AllAppsContainerView extends BaseContainerView implements DragSourc
 
         // IF scroller is at the very top OR there is no scroll bar because there is probably not
         // enough items to scroll, THEN it's okay for the container to be pulled down.
-        if (mAppsRecyclerView.getScrollBar().getThumbOffset().y <= 0) {
+        if (mAppsRecyclerView.getScrollBar().getThumbOffsetY() <= 0) {
             return true;
         }
         return false;