Fixing path to chrome app samples in documentation

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>
 
 <p class="note">
 <b>Samples:</b> For examples that illustrate how Chrome Apps can connect to hardware devices, see the
-<a href="https://github.com/GoogleChrome/chrome-app-samples/tree/master/serial">serial</a>,
-<a href="https://github.com/GoogleChrome/chrome-app-samples/tree/master/servo">servo</a>,
-<a href="https://github.com/GoogleChrome/chrome-app-samples/tree/master/usb">usb</a>, and
-<a href="https://github.com/GoogleChrome/chrome-app-samples/tree/master/zephyr_hxm">zephyr_hxm
+<a href="https://github.com/GoogleChrome/chrome-app-samples/tree/master/samples/serial">serial</a>,
+<a href="https://github.com/GoogleChrome/chrome-app-samples/tree/master/samples/servo">servo</a>,
+<a href="https://github.com/GoogleChrome/chrome-app-samples/tree/master/samples/usb">usb</a>, and
+<a href="https://github.com/GoogleChrome/chrome-app-samples/tree/master/samples/zephyr_hxm">zephyr_hxm
 Bluetooth</a> samples.
 </p>
 
 <p>
   For background information about USB, see the official
   <a href="http://www.usb.org/home">USB specifications</a>. <br/>
   <a href="http://www.beyondlogic.org/usbnutshell/usb1.shtml">
     <i>USB in a NutShell</i></a>
   is a reasonable crash course that you may find helpful.
 </p>
@@ skipping 605 matching lines @@
 };
 chrome.usb.interruptTransfer(connectionHandle, transferInfo, optionalCallback);
 </pre>
 
 <h2 id="caveats">Caveats</h2>
 
 <p>Not all devices can be accessed through the USB API. In general, devices
   are not accessible because either the Operating System's kernel or a native
   driver holds them off from user space code. Some examples are devices with
   HID profiles on OSX systems, and USB pen drives.</p>
-  
+
 <p>
   On most Linux systems, USB devices are mapped with read-only permissions by
   default. To open a device through this API, your user will need to have
   write access to it too.
   A simple solution is to set a udev rule. Create a file
   <code>/etc/udev/rules.d/50-yourdevicename.rules</code>
   with the following content:
 </p>
 
 <pre>
@@ skipping 12 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>