Add UMA metric for "View Original" link clicks in distilled page viewer.

components/dom_distiller/content/resources/dom_distiller_viewer.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 function addToPage(html) {
   var div = document.createElement('div');
   div.innerHTML = html;
   document.getElementById('content').appendChild(div);
 }
 
@@ skipping 47 matching lines @@
         this.colorShuffle = setInterval(function() {
           colorIndex = (colorIndex + 1) % colors.length;
           loader.className = colors[colorIndex];
         }, 600);
       }
     } else if (isLastPage && typeof this.colorShuffle != "undefined") {
       clearInterval(this.colorShuffle);
     }
   };
 }();
+
+// Add a listener to the "View Original" link to report opt-outs.
+document.getElementById('showOriginal').addEventListener('click', function(e) {
+  var img = document.createElement('img');
+  img.src = "/vieworiginal";
+  img.style.display = "none";
+  document.body.appendChild(img);
+}, true);
+