Create special case mobile data slice

Build the special case mobile data slice for general use,
and for the Internet Connectivity Panel. The Slice controls
the default data subscription, and links to the subscriptions
page.

Bug: 117804089
Fixse: 119411534
Test: robotests & test app.

Change-Id: I31b524a8fe3182a244d940848090e97250632f39

src/com/android/settings/slices/SliceBackgroundWorker.java

@@ -59,6 +59,14 @@ public abstract class SliceBackgroundWorker<E> implements Closeable {
         mUri = uri;
     }
 
+    protected Uri getUri() {
+        return mUri;
+    }
+
+    protected Context getContext() {
+        return mContext;
+    }
+
     /**
      * Returns the singleton instance of the {@link SliceBackgroundWorker} for specified {@link Uri}
      * if exists
@@ -151,7 +159,7 @@ public abstract class SliceBackgroundWorker<E> implements Closeable {
     /**
      * Notify that data was updated and attempt to sync changes to the Slice.
      */
-    protected void notifySliceChange() {
+    protected final void notifySliceChange() {
         mContext.getContentResolver().notifyChange(mUri, null);
     }
 }