Add hard clip for overscrolled children to not be visible above QSB.

We lose the RecyclerView fading edge, but this is the simplest/less risky
solution.

Change-Id: I7aa39a33678ed8a9b9cf9f17c9ad8c14707b0299

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

@@ -312,6 +312,11 @@ public class AllAppsContainerView extends SpringRelativeLayout implements DragSo
         }
     }
 
+    @Override
+    public int getCanvasClipTopForOverscroll() {
+        return mHeader.getTop();
+    }
+
     private void rebindAdapters(boolean showTabs) {
         rebindAdapters(showTabs, false /* force */);
     }