Bug 1343707 - Make datetimepopup.xml binding attach lazily. r=mconley

MozReview-Commit-ID: C7LnrxIbU3K

toolkit/content/widgets/datetimepopup.xml

@@ -25,6 +25,8 @@
       <constructor><![CDATA[
         this.mozIntl = Components.classes["@mozilla.org/mozintl;1"]
                                  .getService(Components.interfaces.mozIMozIntl);
+        // Notify DateTimePickerHelper.jsm that binding is ready.
+        this.dispatchEvent(new CustomEvent("DateTimePickerBindingReady"));
       ]]></constructor>
       <method name="loadPicker">
         <parameter name="type"/>