Improving layout and a11y for HID detection OOBE screen.

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

-<div class="step hidden" id="hid-detection" hidden>
+<div class="step hidden" id="hid-detection" hidden role="group"
+    i18n-values="aria-label:hidDetectionInvitation">
   <div class="step-contents">
     <div id="hid-invitation-text" i18n-content="hidDetectionInvitation"></div>
     <div id="hid-prerequisite-msg" i18n-content="hidDetectionPrerequisites">
     </div>
     <div id="hid-mouse-block">
       <div id="hid-mouse-icon-block">
         <img id="hid-mouse-icon" src="chrome://theme/IDR_BLUETOOTH_MOUSE"
             alt="">
         <img id="hid-mouse-tick" src="chrome://theme/IDR_BLUETOOTH_PAIRING_TICK"
             alt="">
       </div>
       <div id="hid-mouse-label">
-        <span id="hid-mouse-label-searching"
+        <span id="hid-mouse-label-searching" aria-live="polite"
             i18n-content="hidDetectionMouseSearching" class="label">
         </span>
-        <span id="hid-mouse-label-connected"
+        <span id="hid-mouse-label-connected" aria-live="polite"
             i18n-content="hidDetectionUSBMouseConnected" class="label">
         </span>
-        <span id="hid-mouse-label-paired"
+        <span id="hid-mouse-label-paired" aria-live="polite"
             i18n-content="hidDetectionBTMousePaired" class="label">
         </span>
       </div>
     </div>
     <div id="hid-keyboard-block">
       <div id="hid-keyboard-icon-block">
         <img id="hid-keyboard-icon" src="chrome://theme/IDR_BLUETOOTH_KEYBOARD"
             alt="">
         <img id="hid-keyboard-tick"
             src="chrome://theme/IDR_BLUETOOTH_PAIRING_TICK" alt="">
       </div>
       <div id="hid-keyboard-label">
-        <span id="hid-keyboard-label-searching"
+        <span id="hid-keyboard-label-searching" aria-live="polite"
             i18n-content="hidDetectionKeyboardSearching" class="label">
         </span>
-        <span id="hid-keyboard-label-connected"
+        <span id="hid-keyboard-label-connected" aria-live="polite"
             i18n-content="hidDetectionUSBKeyboardConnected" class="label">
         </span>
-        <span id="hid-keyboard-label-paired" class="label">
+        <span id="hid-keyboard-label-paired" class="label" aria-live="polite">
         </span>
         <span id="hid-keyboard-label-pairing" class="label"></span>
       </div>
       <div id="hid-keyboard-pincode">
         <div id="hid-keyboard-pincode-sym-1" class="bluetooth-keyboard-button">
         </div>
         <div id="hid-keyboard-pincode-sym-2" class="bluetooth-keyboard-button">
         </div>
         <div id="hid-keyboard-pincode-sym-3" class="bluetooth-keyboard-button">
         </div>
         <div id="hid-keyboard-pincode-sym-4" class="bluetooth-keyboard-button">
         </div>
         <div id="hid-keyboard-pincode-sym-5" class="bluetooth-keyboard-button">
         </div>
         <div id="hid-keyboard-pincode-sym-6" class="bluetooth-keyboard-button">
         </div>
         <div id="hid-keyboard-pincode-sym-7"
             i18n-content="hidDetectionBTEnterKey"
             class="bluetooth-keyboard-button">
         </div>
       </div>
     </div>
   </div>
   <div id="hid-detection-controls" class="step-controls"></div>
 </div>