Chrome OS: Allow default SMT configuration flag in guest mode.

This adds the scheduler-configuration-default flag to the flags that are
allow listed in guest mode.

BUG=b:147685035

Change-Id: Ic2ef8d84ea71857953a3e223e8a0be140f50c035
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2079252
Auto-Submit: Greg Kerr <kerrnel@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#745166}

chrome/browser/chromeos/login/chrome_restart_request.cc

@@ -140,6 +140,7 @@ void DeriveCommandLine(const GURL& start_url,
     ::switches::kPpapiInProcess,
     ::switches::kRemoteDebuggingPort,
     ::switches::kRendererStartupDialog,
+    ::switches::kSchedulerConfigurationDefault,
     ::switches::kTouchDevices,
     ::switches::kTouchEventFeatureDetection,
     ::switches::kTopChromeTouchUi,