Fixing crash upon window manager creation

chrome/browser/ui/ash/multi_user/multi_user_window_manager_chromeos.cc

Index: chrome/browser/ui/ash/multi_user/multi_user_window_manager_chromeos.cc
diff --git a/chrome/browser/ui/ash/multi_user/multi_user_window_manager_chromeos.cc b/chrome/browser/ui/ash/multi_user/multi_user_window_manager_chromeos.cc
index 43e92626217fa1abf39fb7a986b1443f40e369d2..d910c4067a9b0ad36542c1f62c17a9411f2d410f 100644
--- a/chrome/browser/ui/ash/multi_user/multi_user_window_manager_chromeos.cc
+++ b/chrome/browser/ui/ash/multi_user/multi_user_window_manager_chromeos.cc
@@ -215,20 +215,6 @@ MultiUserWindowManagerChromeOS::MultiUserWindowManagerChromeOS(
           message_center::MessageCenter::Get(), current_user_id)),
       suppress_visibility_changes_(false),
       animation_speed_(ANIMATION_SPEED_NORMAL) {
-  // Add a session state observer to be able to monitor session changes.
-  if (ash::Shell::HasInstance())
-    ash::Shell::GetInstance()->session_state_delegate()->
-        AddSessionStateObserver(this);
-
-  // The BrowserListObserver would have been better to use then the old
-  // notification system, but that observer fires before the window got created.
-  registrar_.Add(this, NOTIFICATION_BROWSER_WINDOW_READY,
-                 content::NotificationService::AllSources());
-
-  // Add an app window observer & all already running apps.
-  Profile* profile = multi_user_util::GetProfileFromUserID(current_user_id);
-  if (profile)
-    AddUser(profile);
 }
 
 MultiUserWindowManagerChromeOS::~MultiUserWindowManagerChromeOS() {
@@ -264,6 +250,27 @@ MultiUserWindowManagerChromeOS::~MultiUserWindowManagerChromeOS() {
         RemoveSessionStateObserver(this);
 }
 
+void MultiUserWindowManagerChromeOS::Init() {
+  // We should call this function only once.
+  DCHECK(user_id_to_app_observer_.find(current_user_id_) ==
+             user_id_to_app_observer_.end());

[stevenjb, 2015/02/03 01:31:58]

nit: This only actually ensures that we don't call AddUser more than once, which
will only be true if  multi_user_util::GetProfileFromUserID(current_user_id_)
returns a valid Profile below. We may want to test that first, or at least
clarify the comment a little.

[Mr4D (OOO till 08-26), 2015/02/03 02:06:05]

We add the observer as well - so it is not only the AddUser which gets called in
that special case. Generally speaking an Init function should not get called
several times. But I changed the comment slightly.

+
+  // Add a session state observer to be able to monitor session changes.
+  if (ash::Shell::HasInstance())
+    ash::Shell::GetInstance()->session_state_delegate()->
+        AddSessionStateObserver(this);

[stevenjb, 2015/02/03 01:31:58]

nit: {}

[Mr4D (OOO till 08-26), 2015/02/03 02:06:05]

Done.

+
+  // The BrowserListObserver would have been better to use then the old
+  // notification system, but that observer fires before the window got created.
+  registrar_.Add(this, NOTIFICATION_BROWSER_WINDOW_READY,
+                 content::NotificationService::AllSources());
+
+  // Add an app window observer & all already running apps.
+  Profile* profile = multi_user_util::GetProfileFromUserID(current_user_id_);
+  if (profile)
+    AddUser(profile);
+}
+
 void MultiUserWindowManagerChromeOS::SetWindowOwner(
     aura::Window* window,
     const std::string& user_id) {