Setting Guest last-active for the User Manager doesn't create the Guest.

chrome/browser/ui/cocoa/profiles/user_manager_mac.mm

Index: chrome/browser/ui/cocoa/profiles/user_manager_mac.mm
diff --git a/chrome/browser/ui/cocoa/profiles/user_manager_mac.mm b/chrome/browser/ui/cocoa/profiles/user_manager_mac.mm
index 89fd112b6e3f02c0fede01052ce0d13e800c1569..9452eaef915f75c6352bf33f8912ab4e7c44cc38 100644
--- a/chrome/browser/ui/cocoa/profiles/user_manager_mac.mm
+++ b/chrome/browser/ui/cocoa/profiles/user_manager_mac.mm
@@ -23,6 +23,21 @@
 #include "ui/base/l10n/l10n_util_mac.h"
 #include "ui/events/keycodes/keyboard_codes.h"
 
+namespace {
+
+// Update the App Controller with a new Profile. Used when a Profile is locked
+// to set the Controller to the Guest Profile so the old Profile's bookmarks,
+// etc... cannot be accessed.
+void ChangeAppControllerForProfile(Profile* profile,
+                                   Profile::CreateStatus status) {
+  if (status == Profile::CREATE_STATUS_INITIALIZED) {
+    AppController* controller =
+        base::mac::ObjCCast<AppController>([NSApp delegate]);
+    [controller windowChangedToProfile:profile];
+  }
+}
+
+}  // namespace
 
 // An open User Manager window. There can only be one open at a time. This
 // is reset to NULL when the window is closed.
@@ -141,11 +156,13 @@ class UserManagerWebContentsDelegate : public content::WebContentsDelegate {
   // will not trigger a -windowChangedToProfile and update the menu bar.
   // This is only important if the active profile is Guest, which may have
   // happened after locking a profile.
-  Profile* guestProfile = profiles::SetActiveProfileToGuestIfLocked();
-  if (guestProfile && guestProfile->IsGuestSession()) {
-    AppController* controller =
-        base::mac::ObjCCast<AppController>([NSApp delegate]);
-    [controller windowChangedToProfile:guestProfile];
+  if (profiles::SetActiveProfileToGuestIfLocked()) {
+    g_browser_process->profile_manager()->CreateProfileAsync(
+        ProfileManager::GetGuestProfilePath(),
+        base::Bind(&ChangeAppControllerForProfile),
+        base::string16(),
+        base::string16(),
+        std::string());
   }
   [[self window] makeKeyAndOrderFront:self];
 }