Enable USB device permission for interface class for stable

chrome/common/extensions/docs/templates/articles/app_usb.html

 <h1>USB Devices</h1>
 
 <p>
 This document describes how to use the <a href="usb">USB API</a> to communicate
 with USB devices. Some devices are not accessible through the USB API
 (see the <a href="#caveats">Caveats</a> section below for details).
 Chrome Apps can also connect to <a href="serial">serial</a> and
 <a href="bluetooth">Bluetooth</a> devices.
 </p>
 
@@ skipping 24 matching lines @@
 
 <p>In addition, in order to prevent
   <a href="http://en.wikipedia.org/wiki/Device_fingerprint">finger-printing</a>,
   you must declare all the device types you want to access in the manifest file.
   Each type of USB device corresponds to a vendor id/product id (VID/PID) pair.
   You can use $(ref:usb.getDevices) to enumerate devices by their VID/PID
   pair.
 </p>
 <p>
   You must declare the VID/PID pairs for each type of device you want to use
-  under the "usbDevices" permission in your app's manifest file, as shown in the
-  example below:</p>
+  under the <code>usbDevices</code> permission in your app's manifest file, as
+  shown in the example below:</p>
 
 <pre data-filename="manifest.json">
 "permissions": [
   {
     "usbDevices": [
       {
         "vendorId": 123,
         "productId": 456
       }
     ]
   }
 ]
 </pre>
 
 <p class="note">Note that only decimal numbers are allowed in JSON format.
   You cannot use hexadecimal numbers in these fields.</p>
 
+<p>Since <b>Chrome 57</b>, requirement for declaring all the device types

[Devlin, 2017/01/10 15:56:50]

*the* requirement

[tbarzic, 2017/01/10 17:42:25]

Done.

+  in the app manifest is relaxed for apps running as Chrome OS
+  <a href="apps/manifest/kiosk_enabled">kiosk apps</a>.
+  For kiosk apps, you can use <code>interfaceClass</code> permission property to

[Devlin, 2017/01/10 15:56:50]

*the* <code>interfaceClass....

[tbarzic, 2017/01/10 17:42:25]

Done.

+  declare permission to access USB devices that:

[Devlin, 2017/01/10 15:56:50]

s/declare/request?

[tbarzic, 2017/01/10 17:42:25]

Done.

+  <ul>
+    <li>implement a USB interface of a specific interface class</li>
+    <li>have a specific USB device class</li>
+  </ul>
+  For example, the following <code>usbDevices</code> permission would grant an
+  app access to all USB devices that implement a printer interface (interface
+  class code 7), and to USB hub devices (device class code 9):</p>
+
+<pre data-filename="manifest.json">
+"permissions": [
+  {
+    "usbDevices": [
+      {"interfaceClass": 7},
+      {"interfaceClass": 9}
+    ]
+  }
+]
+</pre>
+
+<p>For list of acceptable <code>interfaceClass</code> values, see

[Devlin, 2017/01/10 15:56:50]

*the* list

[tbarzic, 2017/01/10 17:42:25]

Done.

+  <a href="http://www.usb.org/developers/defined_class">USB Class Codes</a>.
+  </p>
+
+<p><code>interfaceClass</code> property can be combined with
+  <code>vendorId</code> property to get access only to USB devices of a specific
+  vendor, as demonstrated by the following example:</p>
+
+<pre data-filename="manifest.json">
+"permissions": [
+  {
+    "usbDevices": [
+      {
+        "vendorId": 123,
+        "interfaceClass": 7
+      }
+    ]
+  }
+]
+</pre>
+
+<p class="note">Note that <code>usbDevices</code> permissions with
+  <code>interfaceClass</code> property have effect only when the app is running
+  in kiosk session - outside a kiosk session said permissions will be ignored.

[Devlin, 2017/01/10 15:56:50]

s/said/these

[tbarzic, 2017/01/10 17:42:25]

Done.

+  </p>
+
 <h2 id="finding_device">Finding a device</h2>
 
 <p>
   To determine whether one or more specific devices are connected to a user's
   system, use the $(ref:usb.getDevices) method:
 </p>
 
 <pre>
 chrome.usb.getDevices(enumerateDevicesOptions, callback);
 </pre>
@@ skipping 591 matching lines @@
     owned by group "plugdev" and have group write permissions.
   </li>
 </ul>
 
 <p>Your app cannot do this automatically since this this procedure requires root
 access. We recommend that you provide instructions to end-users and link to the
 <a href="#caveats">Caveats</a> section on this page for an explanation.</p>
 
 <p>On Chrome OS, simply call $(ref:usb.requestAccess). The permission
   broker does this for you.</p>