Fixed assets

- Make the background of popup key a full transparent color
- Updated the background mdpi asset of keyboard

Bug: 2975027
Bug: 3048638

Change-Id: I8709a1ca403e5c3f862a8be9be1668d30c7687f8

java/res/layout/keyboard_popup.xml

@@ -32,7 +32,7 @@
             android:layout_alignParentBottom="true"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
-            android:background="@drawable/keyboard_dark_background"
+            android:background="@drawable/btn_keyboard_key_gingerbread_popup"
 
             latin:keyBackground="@drawable/btn_keyboard_key_gingerbread_popup"
             latin:keyHysteresisDistance="0dip"