[omnibox chrome:omnibox]: Remove hidden text for boolean fields.

Previously, boolean fields such as the "Can be default" which display a green
check-mark or red x-mark would additionally contain invisible (CSS font-size 0)
text "true" or "false" in order to allow selecting and copying them.

This CL removes this hidden text as we're no longer supporting selecting and
copying partial outputs.

Bug: 937321
Change-Id: Ic347c3f99d645463c59bc2c15d95aaf9148b2f60
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1496923Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: manuk hovanesian <manukh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#638297}

chrome/browser/resources/omnibox/omnibox_output.js

@@ -753,7 +753,6 @@ cr.define('omnibox_output', function() {
     render_() {
       this.icon_.classList.toggle('check-mark', !!this.value);
       this.icon_.classList.toggle('x-mark', !this.value);
-      this.icon_.textContent = this.value;
     }
 
     get text() {

chrome/browser/resources/omnibox/output_results_group.css

@@ -219,7 +219,6 @@ th {
   background-position: center;
   background-repeat: no-repeat;
   background-size: contain;
-  font-size: 0;
   height: 16px;
   width: 16px;
 }