Replace NOTREACHED() with DCHECK(false) (fixes #3500)

Restores the old behavior of assertion in Debug build only.

libcef/browser/simple_menu_model_impl.cc

@@ -540,7 +540,7 @@ bool CefSimpleMenuModelImpl::SetFontListAt(int index,
 bool CefSimpleMenuModelImpl::VerifyContext() {
   if (base::PlatformThread::CurrentId() != supported_thread_id_) {
     // This object should only be accessed from the thread that created it.
-    NOTREACHED();
+    DCHECK(false);
     return false;
   }