Revert of Makes change_id unsigned

mojo/services/view_manager/ids.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_IDS_H_
 #define MOJO_SERVICES_VIEW_MANAGER_IDS_H_
 
 #include "mojo/services/view_manager/view_manager_export.h"
 
 namespace mojo {
 namespace services {
 namespace view_manager {
 
-typedef uint32_t ChangeId;
-
 // Adds a bit of type safety to node ids.
 struct MOJO_VIEW_MANAGER_EXPORT NodeId {
   NodeId(uint16_t connection_id, uint16_t node_id)
       : connection_id(connection_id),
         node_id(node_id) {}
   NodeId() : connection_id(0), node_id(0) {}
 
   bool operator==(const NodeId& other) const {
     return other.connection_id == connection_id &&
         other.node_id == node_id;
@@ skipping 50 matching lines @@
 
 inline uint32_t ViewIdToTransportId(const ViewId& id) {
   return (id.connection_id << 16) | id.view_id;
 }
 
 }  // namespace view_manager
 }  // namespace services
 }  // namespace mojo
 
 #endif  // MOJO_SERVICES_VIEW_MANAGER_IDS_H_