Ensuring that fast scrolling to predictions scrolls list to the top

- Fixes a long standing issue with fast-scrolling to the predicted apps
  not quite scrolling the list to the top of the screen.
- Fixes an issue where we don’t scroll exactly to the fast scroll 
  position due to rounding
- Also fixes a small issue where the thumb would not update when the 
  fast scroll popup was no longer showing, even while dragging.

Bug: 30023608

Change-Id: I6b5080c6aea521ff03dca24317f0405c02725061

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

@@ -377,10 +377,6 @@ public class AllAppsGridAdapter extends RecyclerView.Adapter<AllAppsGridAdapter.
         return isViewType(viewType, VIEW_TYPE_MASK_ICON);
     }
 
-    public static boolean isPredictionIconViewType(int viewType) {
-        return isViewType(viewType, VIEW_TYPE_PREDICTION_ICON);
-    }
-
     public static boolean isViewType(int viewType, int viewTypeMask) {
         return (viewType & viewTypeMask) != 0;
     }