Session restore by default should account for uninitialized state

chrome/browser/ui/cocoa/window_restore_utils.mm

 // Copyright (c) 2011 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.
 
 #import "chrome/browser/ui/cocoa/window_restore_utils.h"
 
 #import <Foundation/Foundation.h>
 
 #include "base/mac/mac_util.h"
 
 namespace restore_utils {
 
 bool IsWindowRestoreEnabled() {
   if (!base::mac::IsOSLionOrLater())
     return false;
 
   NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
   // The defaults must be synchronized here otherwise a stale value will be
   // returned for an indeterminate amount of time.
   [defaults synchronize];
-  return !![defaults boolForKey:@"NSQuitAlwaysKeepsWindows"];
+
+  // By default, the preference is not set. When it's not, the intrinsic Lion
+  // default (YES) should be returned.
+  NSDictionary* prefs = [defaults dictionaryRepresentation];
+  NSNumber* value = [prefs objectForKey:@"NSQuitAlwaysKeepsWindows"];
+  if (!value)
+    return true;
+
+  return !![value boolValue];
 }
 
 }  // namespace restore_utils