AX: Calendar Picker: Initial day selection should notify ActiveDescendantChanged a11y event.

Source/web/resources/calendarPicker.js

 "use strict";
 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 3501 matching lines @@
     if (highlight) {
         firstDayInHighlight = highlight.firstDay().valueOf();
         lastDayInHighlight = highlight.lastDay().valueOf();
     } else {
         firstDayInHighlight = Infinity;
         lastDayInHighlight = Infinity;
     }
     var currentMonth = this.calendarPicker.currentMonth();
     var firstDayInCurrentMonth = currentMonth.firstDay().valueOf();
     var lastDayInCurrentMonth = currentMonth.lastDay().valueOf();
+    var activeDayCell = null;
     for (var dayString in this._dayCells) {
         var dayCell = this._dayCells[dayString];
         var day = dayCell.day;
         dayCell.setIsToday(Day.createFromToday().equals(day));
         dayCell.setSelected(day >= firstDayInSelection && day <= lastDayInSelection);
         var isHighlighted = day >= firstDayInHighlight && day <= lastDayInHighlight;
         dayCell.setHighlighted(isHighlighted);
         if (isHighlighted && firstDayInHighlight == lastDayInHighlight)
-            this.element.setAttribute("aria-activedescendant", dayCell.element.id);
+            activeDayCell = dayCell;
         dayCell.setIsInCurrentMonth(day >= firstDayInCurrentMonth && day <= lastDayInCurrentMonth);
         dayCell.setDisabled(!this.calendarPicker.isValidDay(day));
     }
     if (this.hasWeekNumberColumn) {
         for (var weekString in this._weekNumberCells) {
             var weekNumberCell = this._weekNumberCells[weekString];
             var week = weekNumberCell.week;
             weekNumberCell.setSelected(selection && selection.equals(week));
             weekNumberCell.setHighlighted(highlight && highlight.equals(week));
             weekNumberCell.setDisabled(!this.calendarPicker.isValid(week));
         }
     }
+    if (activeDayCell) {
+        // Ensure a renderer because an element with no renderer doesn't post
+        // activedescendant events. This shouldn't run in the above |for| loop
+        // to avoid CSS transition.
+        activeDayCell.element.offsetLeft;
+        this.element.setAttribute("aria-activedescendant", activeDayCell.element.id);
+    }
 };
 
 /**
  * @param {!Day} day
  * @return {!DayCell}
  */
 CalendarTableView.prototype.prepareNewDayCell = function(day) {
     var dayCell = DayCell.recycleOrCreate();
     dayCell.reset(day);
     this._dayCells[dayCell.day.toString()] = dayCell;
@@ skipping 501 matching lines @@
         event.stopPropagation();
         event.preventDefault();
     }
 };
 
 if (window.dialogArguments) {
     initialize(dialogArguments);
 } else {
     window.addEventListener("message", handleMessage, false);
 }