Update ActionButtonsPreference style

 - Add rounded background
 - Add divider between buttons
 Screenshots:
   https://screenshot.googleplex.com/5b3fanqgpbpufyD.png
   https://screenshot.googleplex.com/5jG85UeVk64pAMg.png

Bug: 187923403
Test: atest ActionButtonsPreferenceTest
Change-Id: I04bebbfc676c5c5d019a4dce1b8e31bfc69360d7
diff --git a/packages/SettingsLib/ActionButtonsPreference/lint-baseline.xml b/packages/SettingsLib/ActionButtonsPreference/lint-baseline.xml
index a19f7af..22b25a3 100644
--- a/packages/SettingsLib/ActionButtonsPreference/lint-baseline.xml
+++ b/packages/SettingsLib/ActionButtonsPreference/lint-baseline.xml
@@ -23,4 +23,15 @@
             column="15"/>
     </issue>
 
+    <issue
+        id="NewApi"
+        message="`?android:attr/dialogCornerRadius` requires API level 28 (current min is 21)"
+        errorLine1="        android:radius=&quot;?android:attr/dialogCornerRadius&quot;"
+        errorLine2="              ~~~~~~~~~~~~~~~~~~~~~~~~~~~">
+        <location
+            file="frameworks/base/packages/SettingsLib/ActionButtonsPreference/res/drawable/settingslib_rounded_background.xml"
+            line="23"
+            column="9"/>
+    </issue>
+
 </issues>