[Mac] Fix profile getting re-created / IO allowed dcheck with profile menu.

chrome/browser/ui/cocoa/profile_menu_controller.mm

Index: chrome/browser/ui/cocoa/profile_menu_controller.mm
===================================================================
--- chrome/browser/ui/cocoa/profile_menu_controller.mm	(revision 174685)
+++ chrome/browser/ui/cocoa/profile_menu_controller.mm	(working copy)
@@ -175,6 +175,19 @@
   // Tell the model that the browser has changed.
   model_->set_browser(browser);
 
+  // If |browser| is NULL, it may be because the current profile was deleted
+  // and there are no other loaded profiles. In this case, calling
+  // |model_->GetActiveProfileIndex()| may result in a profile being loaded,
+  // which is inappropriate to do on the UI thread.
+  //
+  // An early return provides the desired behavior:
+  //   a) If the profile was deleted, the menu would have been rebuilt and no
+  //      profile will have a check mark.
+  //   b) If the profile was not deleted, but there is no active browser, then
+  //      the previous profile will remain checked.
+  if (!browser)
+    return;
+
   size_t active_profile_index = model_->GetActiveProfileIndex();
 
   // Update the state for the menu items.