[Sync] Add bookmark move tests.

sync/test/fake_server/bookmark_entity.cc

Index: sync/test/fake_server/bookmark_entity.cc
diff --git a/sync/test/fake_server/bookmark_entity.cc b/sync/test/fake_server/bookmark_entity.cc
index b13465f55df6335e2086644e78c60c1e05e63999..7f0b1cb6e10910bb44b670c39b4a031631938a1b 100644
--- a/sync/test/fake_server/bookmark_entity.cc
+++ b/sync/test/fake_server/bookmark_entity.cc
@@ -94,6 +94,10 @@ BookmarkEntity::BookmarkEntity(
   SetSpecifics(specifics);
 }
 
+void BookmarkEntity::SetParentId(string parent_id) {
+  parent_id_ = parent_id;
+}
+
 string BookmarkEntity::GetParentId() const {
   return parent_id_;
 }