Make it clear what last_sync_timestamp actually tracks. Update

chrome/browser/cocoa/preferences_window_controller.h

Index: chrome/browser/cocoa/preferences_window_controller.h
diff --git a/chrome/browser/cocoa/preferences_window_controller.h b/chrome/browser/cocoa/preferences_window_controller.h
index 33fce3ac80a12ae198eafdf7f6f3a4d45aaf73fb..03a8ca51ffae0ad95c97499c7d54f11d12aaee5f 100644
--- a/chrome/browser/cocoa/preferences_window_controller.h
+++ b/chrome/browser/cocoa/preferences_window_controller.h
@@ -24,7 +24,7 @@ class ProfileSyncService;
 // A window controller that handles the preferences window. The bulk of the
 // work is handled via Cocoa Bindings and getter/setter methods that wrap
 // cross-platform PrefMember objects. When prefs change in the back-end
-// (that is, outside of this UI), our observer recieves a notification and can
+// (that is, outside of this UI), our observer receives a notification and can
 // tickle the KVO to update the UI so we are always in sync. The bindings are
 // specified in the nib file. Preferences are persisted into the back-end
 // as they are changed in the UI, and are thus immediately available even while