have "search" as the reason when dismissing system dialogs for search.

this way search can't dismiss itself.  can't use the constant because it is
in policy.  would rather leave it this way instead of moving constants for
system dialog dismissal to framework.

policy/com/android/internal/policy/impl/PhoneWindow.java

@@ -2510,7 +2510,7 @@ public class PhoneWindow extends Window implements MenuBuilder.Callback {
         if (cb == null) {
             return false;
         } else {
-            sendCloseSystemWindows();
+            sendCloseSystemWindows("search");
             return cb.onSearchRequested();
         }
     }