Record NewTabPage.MostVisited histogram on Android.

chrome/browser/resources/ntp_android/ntp_android.js

Index: chrome/browser/resources/ntp_android/ntp_android.js
diff --git a/chrome/browser/resources/ntp_android/ntp_android.js b/chrome/browser/resources/ntp_android/ntp_android.js
index ad62da041f40a9ee09e7da6ae4773ab1205ab1a2..e1cf31ac35b7540d9d1236ce012f3c5b7a545bbe 100644
--- a/chrome/browser/resources/ntp_android/ntp_android.js
+++ b/chrome/browser/resources/ntp_android/ntp_android.js
@@ -943,11 +943,17 @@ cr.define('ntp', function() {
       data.splice(8, data.length - 8);
     }
 
+    data.forEach(function(item, index) {
+      item.mostVisitedIndex = index;
+    });

[Dan Beam, 2013/11/14 04:44:38]

nit: I'd strip off this duplicate/volatile data and just query the DOM, imo:

  /**
   * @param {!HTMLElement} el The most visited element.
   * @return {number} The most visited index of item.
   */
  function mouseVisitedIndex(el) {
    // If they're siblings.
    return Array.prototype.indexOf.call(el.parentNode.childNodes, el);
  }

or something like:

    var all = document.querySelectorAll('.most-visited');
    return Array.prototype.indexOf.call(all, el);

if they're not siblings.  i think this is less error prone.  if this is *really*
bad for performance on mobile, eh, maybe ignore.

[newt (away), 2013/11/14 18:44:02]

If it's OK with you, I think I'll leave this as is. I've already verified the
current solution, and since this code will be deleted soon, I'd prefer not to
spend extra time on it.

[Dan Beam, 2013/11/14 19:16:03]

that's fine.

+
     if (equals(data, mostVisitedData_))
       return;
 
     var clickFunction = function(item) {
       chrome.send('openedMostVisited');
+      chrome.send('metricsHandler:recordInHistogram',
+          ['NewTabPage.MostVisited', item.mostVisitedIndex, 8]);
       window.location = item.url;
     };
     populateData(findList('most_visited'), SectionType.MOST_VISITED, data,
@@ -1204,6 +1210,12 @@ cr.define('ntp', function() {
         case ContextMenuItemIds.MOST_VISITED_OPEN_IN_NEW_TAB:
         case ContextMenuItemIds.MOST_VISITED_OPEN_IN_INCOGNITO_TAB:
           chrome.send('openedMostVisited');
+          if (contextMenuItem != null) {

[Dan Beam, 2013/11/14 04:44:38]

nit: if (contextMenuItem) {

[newt (away), 2013/11/14 18:44:02]

Done.

+            chrome.send('metricsHandler:recordInHistogram',
+                ['NewTabPage.MostVisited',
+                 contextMenuItem.mostVisitedIndex,
+                 8]);
+          }
           break;
 
         case ContextMenuItemIds.RECENTLY_CLOSED_OPEN_IN_NEW_TAB: