Remove shadow animation from button-spinners

Set stateListDrawable=@null on the Buttons.

Bug: 16295904
Change-Id: Iaced0e0ac11ea10ab0d5526429d2f926c8855542
diff --git a/res/layout/edit_date_picker.xml b/res/layout/edit_date_picker.xml
index b84a8d5..ce9a85f 100644
--- a/res/layout/edit_date_picker.xml
+++ b/res/layout/edit_date_picker.xml
@@ -20,7 +20,7 @@
 <Button
     xmlns:android="http://schemas.android.com/apk/res/android"
     android:id="@+id/date_view"
-    style="?android:attr/spinnerStyle"
+    style="@style/SpinnerButtonStyle"
     android:layout_width="0dip"
     android:layout_height="@dimen/editor_min_line_item_height"
     android:layout_weight="1"