cros: Whitelist kRlzPingDelay in kForwardSwitches

This is for the convenience of testing rlz ping. The normal waiting
time is 24 hours and it's unrealistic for testing team.

Bug: 894331
Change-Id: Ia5d6d38bc05221672d4ae4a0b6da4e221aaa0607
Reviewed-on: https://chromium-review.googlesource.com/c/1270012Reviewed-by: Alexander Alekseev <alemate@chromium.org>
Commit-Queue: Wenzhao (Colin) Zang <wzang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#599256}

chrome/browser/chromeos/login/chrome_restart_request.cc

@@ -209,6 +209,7 @@ void DeriveCommandLine(const GURL& start_url,
     chromeos::switches::kHasChromeOSKeyboard,
     chromeos::switches::kLoginProfile,
     chromeos::switches::kNaturalScrollDefault,
+    chromeos::switches::kRlzPingDelay,
     chromeos::switches::kSystemInDevMode,
     policy::switches::kDeviceManagementUrl,
     wm::switches::kWindowAnimationsDisabled,