Don't lose content change during rollback for loader already started

Framework edition

If a loader is already started when we try to rollback a content
change, force a new load instead of simply setting the flag to refresh
next time.

Bug 28406183

https://code.google.com/p/android/issues/detail?id=208278

Change-Id: If11d79088d30dd2dc48cf1b3d2882f3712b6cddb

core/java/android/content/Loader.java

@@ -484,7 +484,7 @@ public class Loader<D> {
      */
     public void rollbackContentChanged() {
         if (mProcessingChange) {
-            mContentChanged = true;
+            onContentChanged();
         }
     }