Improve search indexing time.

- Some import clean up.
- Add timing log to track indexing time breakdown.
- Remove isAvailable() from UserDictionaryPreferenceController.

Bug: 36391685
Test: rebuild
Change-Id: If154c5dafba5d21cb1020497c44fbf67f03ad820

src/com/android/settings/search/SearchFeatureProvider.java

@@ -16,16 +16,12 @@
  */
 package com.android.settings.search;
 
-import android.app.Activity;
 import android.content.Context;
-import android.view.Menu;
 import android.view.View;
 
 import com.android.settings.dashboard.SiteMapManager;
 import com.android.settings.search.ranking.SearchResultsRankerCallback;
 
-import java.util.List;
-
 /**
  * FeatureProvider for Settings Search
  */