Fix tabs scrollbar refreshing issue (#2941)

Author: keianhzo

app/src/common/shared/org/mozilla/vrbrowser/ui/widgets/TabsWidget.java

@@ -323,9 +323,10 @@ private void enterSelectMode() {
         mSelecting = true;
         mSelectTabsButton.setVisibility(View.GONE);
         mDoneButton.setVisibility(View.VISIBLE);
-        mAdapter.notifyDataSetChanged();
         updateSelectionMode();
         mWidgetManager.pushBackHandler(mSelectModeBackHandler);
+
+        post(() -> mAdapter.notifyDataSetChanged());
     }
 
     private void exitSelectMode() {
@@ -336,9 +337,10 @@ private void exitSelectMode() {
         mSelectTabsButton.setVisibility(View.VISIBLE);
         mDoneButton.setVisibility(View.GONE);
         mSelectedTabs.clear();
-        mAdapter.notifyDataSetChanged();
         updateSelectionMode();
         mWidgetManager.popBackHandler(mSelectModeBackHandler);
+
+        post(() -> mAdapter.notifyDataSetChanged());
     }
 
     private void updateSelectionMode() {

app/src/main/res/layout/tabs.xml

@@ -117,7 +117,7 @@
         android:paddingStart="15dp"
         android:paddingEnd="15dp"
         android:layout_marginTop="10dp"
-        android:layout_marginBottom="5dp"
+        android:layout_marginBottom="10dp"
         android:fadingEdgeLength="50dp">
     </org.mozilla.vrbrowser.ui.views.CustomRecyclerView>