diff -r 000000000000 -r 6474c204b198 mobile/android/base/sync/synchronizer/UnexpectedSessionException.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mobile/android/base/sync/synchronizer/UnexpectedSessionException.java	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,26 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.gecko.sync.synchronizer;
+
+import org.mozilla.gecko.sync.SyncException;
+import org.mozilla.gecko.sync.repositories.RepositorySession;
+
+/**
+ * An exception class that indicates that a session was passed
+ * to a begin callback and wasn't expected.
+ *
+ * This shouldn't occur.
+ *
+ * @author rnewman
+ *
+ */
+public class UnexpectedSessionException extends SyncException {
+  private static final long serialVersionUID = 949010933527484721L;
+  public RepositorySession session;
+
+  public UnexpectedSessionException(RepositorySession session) {
+    this.session = session;
+  }
+}