Remove windowNoDisplay from BackgroundOnlyTheme

BackgroundOnlyTheme is only used for .common.vcard activities. These
activities are transparent activities used for launching dialogs
and running tasks. Dialogs require windowNoDisplay=false.

bug: 18163647
Change-Id: I54383e59925e5238a4df30e32be092dfe1e2f1e5
diff --git a/res-common/values/styles.xml b/res-common/values/styles.xml
index 802b8b7..7e1127d 100644
--- a/res-common/values/styles.xml
+++ b/res-common/values/styles.xml
@@ -83,7 +83,9 @@
         <item name="android:windowContentOverlay">@null</item>
         <item name="android:windowAnimationStyle">@null</item>
         <item name="android:windowNoTitle">true</item>
-        <item name="android:windowNoDisplay">true</item>
+        <!-- Activities that use this theme are background activities without obvious displays.
+            However, some also have dialogs. Therefore, it doesn't make sense to set this true.-->
+        <item name="android:windowNoDisplay">false</item>
         <item name="android:windowIsFloating">true</item>
     </style>
 </resources>