Fix -Wimplicit-fallthrough warnings for Chrome OS.

This CL was uploaded by git cl split.

R=skau@chromium.org

Bug: 177475
Change-Id: I791616da62378aadcf548de23fd094c9c1325719
Reviewed-on: https://chromium-review.googlesource.com/899447Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534476}

chrome/browser/chromeos/printing/cups_print_job_notification.cc

@@ -218,6 +218,7 @@ void CupsPrintJobNotification::UpdateNotificationIcon() {
       notification_->set_accent_color(
           message_center::kSystemNotificationColorWarning);
       notification_->set_vector_small_image(kNotificationPrintingWarningIcon);
+      break;
     case CupsPrintJob::State::STATE_NONE:
       break;
   }