ChromeOS OOBE: Add ARIA-labels for OOBE screens.

chrome/browser/resources/chromeos/login/oobe_buttons.html

Index: chrome/browser/resources/chromeos/login/oobe_buttons.html
diff --git a/chrome/browser/resources/chromeos/login/oobe_buttons.html b/chrome/browser/resources/chromeos/login/oobe_buttons.html
index 1455522a47e6ce2647b53746eb4bf15a663bf8dc..31d426b2a950e8b5b1259e6b32cd99ac58e3de22 100644
--- a/chrome/browser/resources/chromeos/login/oobe_buttons.html
+++ b/chrome/browser/resources/chromeos/login/oobe_buttons.html
@@ -37,12 +37,13 @@
   Attributes:
     'disabled' - button is disabled when the attribute is set.
     'inverse' - makes text white and background blue
+    'aria-label' - accessibility label.
 -->
 <dom-module id="oobe-text-button">
   <link rel="stylesheet" href="oobe_text_button.css">
   <template>
     <paper-button id="textButton" on-tap="onClick_" disabled="[[disabled]]"
-        inverse$="[[inverse]]">
+        inverse$="[[inverse]]" aria-label$="[[ariaLabel]]">
       <div id="container"
           class="flex layout horizontal center center-justified self-stretch">
         <content></content>
@@ -61,11 +62,13 @@
 
   Attributes:
     'disabled' - button is disabled when the attribute is set.
+    'aria-label' - accessibility label.
 -->
 <dom-module id="oobe-back-button">
   <link rel="stylesheet" href="oobe_nav_button.css">
   <template>
-    <paper-button id="button" on-tap="onClick_" disabled="[[disabled]]">
+    <paper-button id="button" on-tap="onClick_" disabled="[[disabled]]"
+        aria-label$="[[ariaLabel]]">
       <div class="flex horizontal layout start center">
         <iron-icon icon="oobe-buttons:arrow-back"></iron-icon>
         <div id="text">$i18n{back}</div>
@@ -101,7 +104,7 @@
 <dom-module id="oobe-welcome-secondary-button">
   <link rel="stylesheet" href="oobe_welcome_secondary_button.css">
   <template>
-    <paper-button id="button" aria-label="[[ariaLabel]]">
+    <paper-button id="button" aria-label$="[[ariaLabel]]">
       <div id="container" class="flex layout vertical center self-stretch">
         <div id="subcontainer"
             class="flex layout horizontal center self-stretch">