Bug 1790474 - Onboarding progress bar: aria-valuetext starts with "step 0 out of %aria-valuemax%" r=emcminn

Differential Revision: https://phabricator.services.mozilla.com/D157254

browser/components/newtab/content-src/aboutwelcome/components/MultiStageProtonScreen.jsx

@@ -288,6 +288,8 @@ export class ProtonScreen extends React.PureComponent {
         )
       : "";
 
+    const currentStep = this.props.order + 1;
+
     return (
       <main
         className={`screen ${this.props.id ||
@@ -364,12 +366,12 @@ export class ProtonScreen extends React.PureComponent {
                 }`}
                 data-l10n-id={"onboarding-welcome-steps-indicator2"}
                 data-l10n-args={JSON.stringify({
-                  current: this.props.order,
+                  current: currentStep,
                   total,
                 })}
                 data-l10n-attrs="aria-valuetext"
                 role="meter"
-                aria-valuenow={this.props.order}
+                aria-valuenow={currentStep}
                 aria-valuemin={1}
                 aria-valuemax={total}
               >