Provide siblings in a sorted orders in DocumentsUI.

Bug: 27192158
Change-Id: Idefd2ba3027cd4630fcd2aefade9e6b4952e7125
diff --git a/src/com/android/documentsui/dirlist/Model.java b/src/com/android/documentsui/dirlist/Model.java
index 075b3ea..3a45995 100644
--- a/src/com/android/documentsui/dirlist/Model.java
+++ b/src/com/android/documentsui/dirlist/Model.java
@@ -33,7 +33,6 @@
 import android.support.annotation.VisibleForTesting;
 import android.util.Log;
 
-import com.android.documentsui.BaseActivity.SiblingProvider;
 import com.android.documentsui.DirectoryResult;
 import com.android.documentsui.RootCursorWrapper;
 import com.android.documentsui.dirlist.MultiSelectManager.Selection;
@@ -48,7 +47,7 @@
  * The data model for the current loaded directory.
  */
 @VisibleForTesting
-public class Model implements SiblingProvider {
+public class Model {
     private static final String TAG = "Model";
 
     private boolean mIsLoading;
@@ -358,7 +357,7 @@
         return (l == -1) ? Long.MAX_VALUE : l;
     }
 
-    @Nullable Cursor getItem(String modelId) {
+    public @Nullable Cursor getItem(String modelId) {
         Integer pos = mPositions.get(modelId);
         if (pos != null) {
             mCursor.moveToPosition(pos);
@@ -388,14 +387,6 @@
         return docs;
     }
 
-    @Override
-    public Cursor getCursor() {
-        if (Looper.myLooper() != Looper.getMainLooper()) {
-            throw new IllegalStateException("Can't call getCursor from non-main thread.");
-        }
-        return mCursor;
-    }
-
     void addUpdateListener(UpdateListener listener) {
         mUpdateListeners.add(listener);
     }