Allow for keyboard navigation down chips list

Replace the old dropdown background with simply selectableItem
because the autocomplete list doesn't require states such as
activated (mostly used for alt/single recipient popup).

b/17322127

Change-Id: I742850854f568852c7b1f5fdf2a6bca247ba3b59
diff --git a/res/layout/chips_autocomplete_recipient_dropdown_item.xml b/res/layout/chips_autocomplete_recipient_dropdown_item.xml
index d15a97b..ec512c2 100644
--- a/res/layout/chips_autocomplete_recipient_dropdown_item.xml
+++ b/res/layout/chips_autocomplete_recipient_dropdown_item.xml
@@ -18,6 +18,7 @@
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
+    android:background="?android:attr/selectableItemBackground"
     android:minHeight="@dimen/chip_dropdown_height"
     android:orientation="vertical">
 
@@ -28,7 +29,6 @@
     <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
-        android:background="@drawable/chips_dropdown_background"
         style="@style/ChipAutocompleteWrapperStyle">
 
         <LinearLayout style="@style/ChipTextViewLayoutStyle">
diff --git a/res/values/styles.xml b/res/values/styles.xml
index 2e7d6b4..5c7dcec 100644
--- a/res/values/styles.xml
+++ b/res/values/styles.xml
@@ -13,15 +13,14 @@
      See the License for the specific language governing permissions and
      limitations under the License.
 -->
-<resources xmlns:tools="http://schemas.android.com/tools"
-           xmlns:xliff="urn:oasis:names:tc:xliff:document:1.2">
+<resources xmlns:tools="http://schemas.android.com/tools">
     <style name="RecipientEditTextViewBase" parent="@android:attr/autoCompleteTextViewStyle">
         <item name="android:layout_width">match_parent</item>
         <item name="android:layout_height">wrap_content</item>
         <item name="android:background">@null</item>
         <item name="android:inputType">textEmailAddress|textMultiLine</item>
         <item name="android:minHeight">@dimen/chip_height</item>
-        <item name="android:popupBackground">@null</item>
+        <item name="android:popupBackground">@android:color/white</item>
         <item name="android:textAlignment" tools:ignore="NewApi">viewStart</item>
         <item name="android:textAppearance">?android:attr/textAppearanceMedium</item>
         <item name="android:textDirection" tools:ignore="NewApi">locale</item>