Cleans up usage of ViewManagerServiceImpl::roots_

mojo/services/public/cpp/view_manager/lib/view_manager_client_impl.cc

Index: mojo/services/public/cpp/view_manager/lib/view_manager_client_impl.cc
diff --git a/mojo/services/public/cpp/view_manager/lib/view_manager_client_impl.cc b/mojo/services/public/cpp/view_manager/lib/view_manager_client_impl.cc
index a9bb119b762150cb905d4247fef97fbbbe076331..d4dbfe427e4133327e67835b1e848b9aea9a94fe 100644
--- a/mojo/services/public/cpp/view_manager/lib/view_manager_client_impl.cc
+++ b/mojo/services/public/cpp/view_manager/lib/view_manager_client_impl.cc
@@ -59,10 +59,13 @@ Node* AddNodeToViewManager(ViewManagerClientImpl* client,
 }
 
 Node* BuildNodeTree(ViewManagerClientImpl* client,
-                    const Array<NodeDataPtr>& nodes) {
+                    const Array<NodeDataPtr>& nodes,
+                    Node* initial_parent) {
   std::vector<Node*> parents;
   Node* root = NULL;
   Node* last_node = NULL;
+  if (initial_parent)
+    parents.push_back(initial_parent);
   for (size_t i = 0; i < nodes.size(); ++i) {
     if (last_node && nodes[i]->parent_id == last_node->id()) {
       parents.push_back(last_node);
@@ -324,11 +327,11 @@ void ViewManagerClientImpl::OnViewManagerConnectionEstablished(
   connected_ = true;
   connection_id_ = connection_id;
   creator_url_ = TypeConverter<String, std::string>::ConvertFrom(creator_url);
-  AddRoot(BuildNodeTree(this, nodes));
+  AddRoot(BuildNodeTree(this, nodes, NULL));
 }
 
 void ViewManagerClientImpl::OnRootAdded(Array<NodeDataPtr> nodes) {
-  AddRoot(BuildNodeTree(this, nodes));
+  AddRoot(BuildNodeTree(this, nodes, NULL));
 }
 
 void ViewManagerClientImpl::OnNodeBoundsChanged(Id node_id,
@@ -344,7 +347,10 @@ void ViewManagerClientImpl::OnNodeHierarchyChanged(
     Id new_parent_id,
     Id old_parent_id,
     mojo::Array<NodeDataPtr> nodes) {
-  BuildNodeTree(this, nodes);
+  Node* initial_parent = nodes.size() ?
+      GetNodeById(nodes[0]->parent_id) : NULL;
+
+  BuildNodeTree(this, nodes, initial_parent);
 
   Node* new_parent = GetNodeById(new_parent_id);
   Node* old_parent = GetNodeById(old_parent_id);