Show wallpaper as background for WifiSetupActivity

b/62571086

Before this change, WifiSetupActivity's UI was overlaying atop whichever
Activity was below it in the task, so the user saw two Activities at the
same time. With this change, the Activity is now properly backed by the
wallpaper, and can now safely be shown atop other Activities.

test: manual
Change-Id: If166db5f8f8f3423aad6fc9f8d385937033b9f5d
diff --git a/Settings/res/values/styles.xml b/Settings/res/values/styles.xml
index 108d92e..2a71329 100644
--- a/Settings/res/values/styles.xml
+++ b/Settings/res/values/styles.xml
@@ -55,8 +55,8 @@
         <item name="wifi_signal_color">@color/setup_list_item</item>
         <item name="wps_color">@color/setup_list_item</item>
         <item name="android:windowBackground">@android:color/transparent</item>
-        <item name="android:windowIsTranslucent">true</item>
         <item name="android:windowAnimationStyle">@style/SetupWindowAnimationStyle</item>
+        <item name="android:windowShowWallpaper">true</item>
     </style>
 
     <style name="Theme.Settings.Transparent">