[NTP4] Track the position of each app that's launched.

chrome/browser/resources/ntp4/apps_page.js

 // Copyright (c) 2012 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.
 
 cr.define('ntp4', function() {
   'use strict';
 
   var localStrings = new LocalStrings;
 
   var APP_LAUNCH = {
@@ skipping 457 matching lines @@
      */
     onClick_: function(e) {
       var is_promo = this.appsPromoExtras_ &&
           window.getComputedStyle(this.appsPromoExtras_).display != 'none';
       var url = !this.appData_.is_webstore ? '' :
           is_promo ? this.appsPromoLink_.href :
                      appendParam(this.appData_.url,
                                  'utm_source',
                                  'chrome-ntp-icon');
 
+      this.recordAppLaunchedFromIndex_();
       chrome.send('launchApp',
                   [this.appId, APP_LAUNCH.NTP_APPS_MAXIMIZED, url,
                    e.button, e.altKey, e.ctrlKey, e.metaKey, e.shiftKey]);
 
       // Don't allow the click to trigger a link or anything
       e.preventDefault();
     },
 
     /**
      * Invoked when the user presses a key while the app is focused.
      * @param {Event} e The key event.
      * @private
      */
     onKeydown_: function(e) {
       if (e.keyIdentifier == 'Enter') {
+        this.recordAppLaunchedFromIndex_();
         chrome.send('launchApp',
                     [this.appId, APP_LAUNCH.NTP_APPS_MAXIMIZED, '',
                      0, e.altKey, e.ctrlKey, e.metaKey, e.shiftKey]);
         e.preventDefault();
         e.stopPropagation();
       }
     },
 
     /**
+     * Records the index of an app when launched.
+     * @private
+     */
+    recordAppLaunchedFromIndex_: function() {
+      var page = this.tile.tilePage;
+      var wide = page.layoutValues.numRowTiles == page.gridValues.maxColCount;
+      chrome.send('recordAppLaunchedFromIndex', [this.tile.index, wide]);
+    },
+
+    /**
      * Adds a node to the list of targets that will launch the app. This list
      * is also used in onMousedown to determine whether the app contents should
      * be shown as active (if we don't do this, then clicking anywhere in
      * appContents, even a part that is outside the ideally clickable region,
      * will cause the app icon to look active).
      * @param {HTMLElement} node The node that should be clickable.
      */
     addLaunchClickTarget_: function(node) {
       node.classList.add('launch-click-target');
       node.addEventListener('click', this.onClick_.bind(this));
@@ skipping 382 matching lines @@
     appNotificationChanged: appNotificationChanged,
     AppsPage: AppsPage,
     launchAppAfterEnable: launchAppAfterEnable,
   };
 });
 
 // TODO(estade): update the content handlers to use ntp namespace instead of
 // making these global.
 var appNotificationChanged = ntp4.appNotificationChanged;
 var launchAppAfterEnable = ntp4.launchAppAfterEnable;