Fix accessibility issues on most visited page for android's NTP.

Do not modify the DOM of the most visited page if nothing has changed, which
is often the case as the top sites are polled periodically just to make sure
they are up to date.

Also, moves the event listener to a node with a text attribute that allows it
to be selected in accessibility mode.

Makes some markup nodes as skippable in accessibility mode by marking them as
having empty alt text.

BUG=155450


Review URL: https://chromiumcodereview.appspot.com/11155022

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@162246 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/resources/ntp_android/ntp_android.js

@@ -324,6 +324,12 @@ cr.define('ntp', function() {
    */
   var syncEnabled = undefined;
 
+  /**
+   * The current most visited data being displayed.
+   * @type {Array.<Object>}
+   */
+  var mostVisitedData_ = [];
+
   /**
    * The current bookmark data being displayed. Keep a reference to this data
    * in case the sync enabled state changes.  In this case, the bookmark data
@@ -655,10 +661,11 @@ cr.define('ntp', function() {
     var title = createDiv('title');
     title.textContent = item.title;
     var spacerImg = createElement('img', 'title-spacer');
+    spacerImg.alt = '';
     title.insertBefore(spacerImg, title.firstChild);
     thumbnailCell.appendChild(title);
 
-    wrapClickHandler(thumbnailContainer, item, opt_clickCallback);
+    wrapClickHandler(thumbnailCell, item, opt_clickCallback);
 
     thumbnailCell.setAttribute(CONTEXT_MENU_URL_KEY, item.url);
     thumbnailCell.contextMenuItem = item;
@@ -910,6 +917,9 @@ cr.define('ntp', function() {
       data.splice(8, data.length - 8);
     }
 
+    if (equals(data, mostVisitedData_))
+      return;
+
     var clickFunction = function(item) {
       chrome.send('metricsHandler:recordAction', ['MobileNTPMostVisited']);
       window.location = item.url;
@@ -917,6 +927,8 @@ cr.define('ntp', function() {
     populateData(findList('most_visited'), SectionType.MOST_VISITED, data,
         makeMostVisitedItem, clickFunction);
     computeDynamicLayout();
+
+    mostVisitedData_ = data;
   }
 
   /**
@@ -2489,6 +2501,31 @@ cr.define('ntp', function() {
 //Utility Functions.
 /////////////////////////////////////////////////////////////////////////////
 
+/**
+ * A best effort approach for checking simple data object equality.
+ * @param {?} val1 The first value to check equality for.
+ * @param {?} val2 The second value to check equality for.
+ * @return {boolean} Whether the two objects are equal(ish).
+ */
+function equals(val1, val2) {
+  if (typeof val1 != 'object' || typeof val2 != 'object')
+    return val1 === val2;
+
+  // Object and array equality checks.
+  var keyCountVal1 = 0;
+  for (var key in val1) {
+    if (!(key in val2) || !equals(val1[key], val2[key]))
+      return false;
+    keyCountVal1++;
+  }
+  var keyCountVal2 = 0;
+  for (var key in val2)
+    keyCountVal2++;
+  if (keyCountVal1 != keyCountVal2)
+    return false;
+  return true;
+}
+
 /**
  * Alias for document.getElementById.
  * @param {string} id The ID of the element to find.