Add instructions for changing locale in Chrome OS to chrome.i18n docs.

Change-Id: I0f8b8e40e39a9f05c58d410a724a5161aae0101b
Reviewed-on: https://chromium-review.googlesource.com/c/1256324
Commit-Queue: Bugs Nash <bugsnash@chromium.org>
Reviewed-by: Meggin Kearney <mkearney@chromium.org>
Cr-Commit-Position: refs/heads/master@{#599789}

chrome/common/extensions/docs/templates/intros/i18n.html

@@ -353,8 +353,9 @@ see the label "Colores" and the extension name "Hola mundo".
 To test translations, you might want to set your browser's locale.
 This section tells you how to set the locale in
 <a href="#testing-win">Windows</a>,
-<a href="#testing-mac">Mac OS X</a>, and
-<a href="#testing-linux">Linux</a>.
+<a href="#testing-mac">Mac OS X</a>,
+<a href="#testing-linux">Linux</a>, and
+<a href="#testing-chromeos">Chrome OS</a>.
 </p>
 
 <h4 id="testing-win">Windows</h4>
@@ -478,6 +479,21 @@ LANGUAGE=es ./chrome
 </pre>
 
 
+<h4 id="testing-chromeos">Chrome OS</h4>
+
+<p>
+To change the locale on Chrome OS:
+</p>
+
+<ol>
+  <li>From the system tray, choose <b>Settings</b>.</li>
+  <li>Under the <b>Languages and input</b> section, choose the <b>Language</b> dropdown.</li>
+  <li>If your language is not listed, click <b>Add languages</b> and add it.</li>
+  <li>Once added, click the the 3-dot <b>More actions</b> menu item next to your language and choose <b>Display Chrome OS in this language</b>.</li>
+  <li>Click the <b>Restart</b> button that appears next to the set language to restart Chrome OS.</li>
+</ol>
+
+
 <h2 id="overview-examples">Examples</h2>
 
 <p>