Don't use dim behind for the search box.

This causes ugly artifacts, such as when dismissing, the full white
completions window disappears into the dimmed background and then
the dimmed background immediately starts undimming.  Likewise when
being displayed, the content behind dims down and then the full
white completions window appears on top.

Change-Id: Id33fb7a172796412143d84e4b3d8915624565f7d
diff --git a/core/res/res/values/themes.xml b/core/res/res/values/themes.xml
index 9e19c57..6dae8b8 100644
--- a/core/res/res/values/themes.xml
+++ b/core/res/res/values/themes.xml
@@ -471,7 +471,6 @@
 
     <!-- Theme for the search input bar. -->
     <style name="Theme.SearchBar" parent="Theme.Panel">
-        <item name="android:backgroundDimEnabled">true</item>
         <item name="windowContentOverlay">@null</item>        
     </style>