Change userid from a uint32_t to a string guid

components/mus/ws/user_id_tracker.cc

 // Copyright 2016 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.
 
 #include "components/mus/ws/user_id_tracker.h"
 
 #include "components/mus/ws/user_id_tracker_observer.h"
 #include "mojo/shell/public/interfaces/connector.mojom.h"
 
 namespace mus {
 namespace ws {
 
 UserIdTracker::UserIdTracker()
-    : active_id_(mojo::shell::mojom::Connector::kInvalidApplicationID) {}
+    : active_id_(mojo::shell::mojom::kRootUserID) {}
 UserIdTracker::~UserIdTracker() {
   DCHECK(ids_.empty());
 }
 
-bool UserIdTracker::IsValidUserId(UserId id) const {
+bool UserIdTracker::IsValidUserId(const UserId& id) const {
   return ids_.count(id) > 0;
 }
 
-void UserIdTracker::SetActiveUserId(UserId id) {
+void UserIdTracker::SetActiveUserId(const UserId& id) {
   if (id == active_id_)
     return;
 
   active_id_ = id;
   FOR_EACH_OBSERVER(UserIdTrackerObserver, observers_,
                     OnActiveUserIdChanged(id));
 }
 
-void UserIdTracker::AddUserId(UserId id) {
+void UserIdTracker::AddUserId(const UserId& id) {
   DCHECK(!IsValidUserId(id));
   ids_.insert(id);
   FOR_EACH_OBSERVER(UserIdTrackerObserver, observers_, OnUserIdAdded(id));
 }
 
-void UserIdTracker::RemoveUserId(UserId id) {
+void UserIdTracker::RemoveUserId(const UserId& id) {
   DCHECK(IsValidUserId(id));
   ids_.erase(id);
   FOR_EACH_OBSERVER(UserIdTrackerObserver, observers_, OnUserIdRemoved(id));
 }
 
 void UserIdTracker::AddObserver(UserIdTrackerObserver* observer) {
   observers_.AddObserver(observer);
 }
 
 void UserIdTracker::RemoveObserver(UserIdTrackerObserver* observer) {
   observers_.RemoveObserver(observer);
 }
 
 }  // namespace ws
 }  // namespace mus