Scroll AllApps to top when new padding is set.

Bug: 198212488
Test: presubmit
Change-Id: I084939e3c7685531c56b1478887fd872e0e101e9

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

@@ -47,6 +47,8 @@ public interface FloatingHeaderRow {
 
     /**
      * Scrolls the content vertically.
+     * @param scroll scrolled distance in pixels for active recyclerview.
+     * @param isScrolledOut bool to determine if row is scrolled out of view
      */
     void setVerticalScroll(int scroll, boolean isScrolledOut);