Cleans up usage of ViewManagerServiceImpl::roots_

mojo/services/view_manager/view_manager_service_impl.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_SERVICES_VIEW_MANAGER_VIEW_MANAGER_SERVICE_IMPL_H_
 #define MOJO_SERVICES_VIEW_MANAGER_VIEW_MANAGER_SERVICE_IMPL_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 217 matching lines @@
   scoped_ptr<AccessPolicy> access_policy_;
 
   // The nodes and views created by this connection. This connection owns these
   // objects.
   NodeMap node_map_;
   ViewMap view_map_;
 
   // The set of nodes that has been communicated to the client.
   NodeIdSet known_nodes_;
 
-  // This is the set of nodes the connection can parent nodes to (in addition to
-  // any nodes created by this connection). If empty the connection can
-  // manipulate any nodes (except for deleting other connections nodes/views).
-  // The connection can not delete or move these. If this is set to a non-empty
-  // value and all the nodes are deleted (by another connection), then an
-  // invalid node is added here to ensure this connection is still constrained.
+  // Set of root nodes from other connections. More specifically any time
+  // Embed() is invoked the id of the node is added to this set for the child
+  // connection. The connection Embed() was invoked on (the parent) doesn't
+  // directly track which connections are attached to which of its nodes. That
+  // information can be found by looking through the |roots_| of all
+  // connections.
   NodeIdSet roots_;
 
   // See description above setter.
   bool delete_on_connection_error_;
 
   DISALLOW_COPY_AND_ASSIGN(ViewManagerServiceImpl);
 };
 
 #if defined(OS_WIN)
 #pragma warning(pop)
 #endif
 
 }  // namespace service
 }  // namespace mojo
 
 #endif  // MOJO_SERVICES_VIEW_MANAGER_VIEW_MANAGER_SERVICE_IMPL_H_