Remove 'Enable tap-to-click' checkbox for non-touchpad devices.

chrome/browser/resources/options/chromeos/system_options.html

 <div id="systemPage" class="page" hidden>
   <h1 i18n-content="systemPage"></h1>
   <div class="displaytable">
     <section>
       <h3 i18n-content="datetimeTitle"></h3>
       <div class="option-control-table">
         <span class="option-name" i18n-content="timezone"></span>
         <div id="timezone-value">
           <select id="timezone-select" class="control"
               i18n-options="timezoneList"
@@ skipping 18 matching lines @@
           <div id="slider-control">
             <input id="sensitivity-range" type="range" min="1" max="5"
                 pref="settings.touchpad.sensitivity2" class="touch-slider">
             <div>
               <span i18n-content="sensitivityLess"></span>
               <span i18n-content="sensitivityMore"
                   class="touchpad-sensitivity-more"></span>
             </div>
           </div>
         </div>
-        <div class="checkbox">
+        <div id="tap-to-click" class="checkbox">
           <label>
             <input id="tap-to-click-check"
                 pref="settings.touchpad.enable_tap_to_click"
                 type="checkbox">
             <span i18n-content="enableTapToClick"></span>
           </label>
         </div>
       </div>  
     </section>
     <!-- By default, the bluetooth section is hidden.  It is only
@@ skipping 44 matching lines @@
             <label>
               <input id="accesibility-check" type="checkbox">
               <span i18n-content="accessibility"></span>
             </label>
           </div>
         </div>
       </div>
     </section>
   </div>
 </div>