Prevent race conditions after dropping database

Block all loaders from accessing the database
before indexing is complete.

Bug: 37501479
Test: make RunSettingsRoboTests
Change-Id: I2af98dcf6bceacbeffa70bd40879c97bb0cbc828
Merged-In: I02f8423c0ffc27abbb8ceb61a8c47d2f0796d0bb

src/com/android/settings/search2/SearchFeatureProvider.java

@@ -21,6 +21,7 @@ import android.view.Menu;
 
 import android.view.View;
 import com.android.settings.dashboard.SiteMapManager;
+import com.android.settings.search.IndexingCallback;
 
 /**
  * FeatureProvider for Settings Search
@@ -68,7 +69,12 @@ public interface SearchFeatureProvider {
     /**
      * Updates the Settings indexes
      */
-    void updateIndex(Context context);
+    void updateIndex(Context context, IndexingCallback callback);
+
+    /**
+     * @returns true when indexing is complete.
+     */
+    boolean isIndexingComplete(Context context);
 
     /**
      * Initializes the feedback button in case it was dismissed.