Improve Search results highlighting

- remove unnecessary code
- use keyed Tag with a well known App key for preventing collisions
- fix missing Brightness Level preference key (used for highlight)

Change-Id: I070e3b8c3cb43da7addd34be192aade21951f57c
diff --git a/src/com/android/settings/HighlightingFragment.java b/src/com/android/settings/HighlightingFragment.java
index 1424abd..4a233b4 100644
--- a/src/com/android/settings/HighlightingFragment.java
+++ b/src/com/android/settings/HighlightingFragment.java
@@ -116,7 +116,7 @@
     }
 
     private boolean checkTag(View view, String key) {
-        final Object tag = view.getTag();
+        final Object tag = view.getTag(R.id.preference_highlight_key);
         if (tag == null || !(tag instanceof String)) {
             return false;
         }