Oobe: clear input field errors upon offline gaia reset

Fixed: 1097739
Change-Id: Ic10887517d34390de9a05e00073d537d9f25bdbd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2260653
Auto-Submit: Denis Kuznetsov [CET] <antrim@chromium.org>
Commit-Queue: Renato Silva <rrsilva@google.com>
Reviewed-by: Renato Silva <rrsilva@google.com>
Cr-Commit-Position: refs/heads/master@{#781785}

chrome/browser/resources/chromeos/login/offline_gaia.js

@@ -97,6 +97,8 @@
       this.domain = '';
       this.email_ = '';
       this.fullEmail_ = '';
+      this.$.emailInput.isInvalid = false;
+      this.$.passwordInput.isInvalid = false;
     },
 
     onForgotPasswordClicked_() {