Add a very basic PIN UI implementation that is shared between lock and settings.

chrome/browser/resources/settings/people_page/people_page.html

Index: chrome/browser/resources/settings/people_page/people_page.html
diff --git a/chrome/browser/resources/settings/people_page/people_page.html b/chrome/browser/resources/settings/people_page/people_page.html
index 7565ad770469f089982a1dc0f421a0aa39c476ad..745199f68ab2f612fb9e38a6fab17ab7d8b9fedd 100644
--- a/chrome/browser/resources/settings/people_page/people_page.html
+++ b/chrome/browser/resources/settings/people_page/people_page.html
@@ -15,6 +15,7 @@
 
 <if expr="chromeos">
 <link rel="import" href="chrome://md-settings/people_page/change_picture.html">
+<link rel="import" href="chrome://md-settings/people_page/pin.html">
 <link rel="import" href="chrome://md-settings/people_page/easy_unlock_browser_proxy.html">
 <link rel="import" href="chrome://md-settings/people_page/easy_unlock_turn_off_dialog.html">
 <link rel="import" href="chrome://md-settings/people_page/users_page.html">
@@ -101,6 +102,15 @@
         </template>
 
 <if expr="chromeos">

[tommycli, 2016/05/02 16:11:27]

Since below is also <if expr="chromeos"> you can combine both blocks.

To confirm - have you checked with UX to determine if this should go above or
below the Easy Unlock settings box?

[jdufault, 2016/05/03 19:21:58]

I combined the blocks and added a TODO.

+        <template is="dom-if" if=[[pinUnlockAllowed_]]>
+          <div class="settings-box">
+            <p>Quick Unlock PIN</p>

[tommycli, 2016/05/02 16:11:27]

i18n

[jdufault, 2016/05/03 19:21:58]

Added a TODO.

+            <pin-keyboard></pin-keyboard>
+          </div>
+        </template>
+</if>
+
+<if expr="chromeos">
         <div class="settings-box">
           <settings-checkbox pref="{{prefs.settings.enable_screen_lock}}"
               i18n-values="label:enableScreenlock">