Fix projection permission dialog layering

Bug: 18392920
Change-Id: I32c2c61339cbea9edd4a7a3f80365213fb4a69ac
diff --git a/packages/SystemUI/res/values/styles.xml b/packages/SystemUI/res/values/styles.xml
index 8d1e9671..09b240b 100644
--- a/packages/SystemUI/res/values/styles.xml
+++ b/packages/SystemUI/res/values/styles.xml
@@ -262,4 +262,14 @@
     <style name="UserDetailView">
         <item name="numColumns">3</item>
     </style>
+
+    <style name="Theme.AlertDialogHost" parent="android:Theme.DeviceDefault">
+        <item name="android:windowIsTranslucent">true</item>
+        <item name="android:windowBackground">@android:color/transparent</item>
+        <item name="android:windowContentOverlay">@null</item>
+        <item name="android:windowNoTitle">true</item>
+        <item name="android:windowIsFloating">true</item>
+        <item name="android:backgroundDimEnabled">false</item>
+        <item name="android:alertDialogTheme">@style/Theme.SystemUI.Dialog.Alert</item>
+    </style>
 </resources>