Allow EmbedRoot to be called multiple times.

mojo/services/view_manager/test_change_tracker.h

Index: mojo/services/view_manager/test_change_tracker.h
diff --git a/mojo/services/view_manager/test_change_tracker.h b/mojo/services/view_manager/test_change_tracker.h
index d597c6faacbd040928d058c7269c256ab192d700..a1d501062a1da8f732ec96bdb3a94d2d391284bf 100644
--- a/mojo/services/view_manager/test_change_tracker.h
+++ b/mojo/services/view_manager/test_change_tracker.h
@@ -27,6 +27,7 @@ enum ChangeType {
   CHANGE_TYPE_VIEW_DELETED,
   CHANGE_TYPE_VIEW_REPLACED,
   CHANGE_TYPE_INPUT_EVENT,
+  CHANGE_TYPE_EMBED_ROOT,
 };
 
 // TODO(sky): consider nuking and converting directly to NodeData.
@@ -57,6 +58,7 @@ struct Change {
   gfx::Rect bounds2;
   int32 event_action;
   String creator_url;
+  String embed_url;
   OrderDirection direction;
 };
 
@@ -111,6 +113,7 @@ class TestChangeTracker {
   void OnViewDeleted(Id view_id);
   void OnNodeViewReplaced(Id node_id, Id new_view_id, Id old_view_id);
   void OnViewInputEvent(Id view_id, EventPtr event);
+  void OnEmbedRoot(const String& url);
 
  private:
   void AddChange(const Change& change);