Files app: Visual Signals move focus to .xf-panel-text

Change the tabindex=0 from .xf-panel-label-text to its parent
.xf-panel-text to have the .xf-panel-secondary-text content included in
the a11y for Chromevox.

This makes the estimated time progress available to screen reader users.

Bug: 1086053
Change-Id: Id39560b2249fb12ff4f49fb39c7439746fc1271c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2494400
Auto-Submit: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Alex Danilo <adanilo@chromium.org>
Commit-Queue: Alex Danilo <adanilo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#820123}

ui/file_manager/file_manager/foreground/elements/xf_panel_item.js

@@ -218,8 +218,8 @@ class PanelItem extends HTMLElement {
             <div class='xf-panel-item'>
                 <xf-circular-progress id='indicator'>
                 </xf-circular-progress>
-                <div class='xf-panel-text' role='alert'>
-                    <span class='xf-panel-label-text' tabindex='0'>
+                <div class='xf-panel-text' role='alert' tabindex='0'>
+                    <span class='xf-panel-label-text'>
                     </span>
                     <br class='xf-linebreaker'/>
                 </div>