Should have more description what isenabled API can do.

[zzhengjian]

As the code below in atoms, there're only few types of elements that support Disabled_Attribue
https://github.com/SeleniumHQ/selenium/blob/1721e627e3b5ab90a06e82df1b088a33a8d11c20/javascript/atoms/dom.js
/**

• List of elements that support the "disabled" attribute, as defined by the
• HTML 4.01 specification.
• @Private {!Array.<goog.dom.TagName>}
• @const
• @see http://www.w3.org/TR/html401/interact/forms.html#h-17.12.1
  */
  bot.dom.DISABLED_ATTRIBUTE_SUPPORTED_ = [
  goog.dom.TagName.BUTTON,
  goog.dom.TagName.INPUT,
  goog.dom.TagName.OPTGROUP,
  goog.dom.TagName.OPTION,
  goog.dom.TagName.SELECT,
  goog.dom.TagName.TEXTAREA
  ];

Can we describe the API doc with more details, so the selenium users wouldn't get confused when calling this function?
https://github.com/SeleniumHQ/selenium/edit/master/java/client/src/org/openqa/selenium/WebElement.java