Bug 972312 part 1.  Generate virtual As*Event functions on WebIDL events so that we can easily go from an nsDOMEvent to the relevant event subtype.  r=smaug
Bug 972312 part 2.  Get rid of InternalScriptErrorEvent and just use mozilla::dom::ErrorEvent for the cases that used to use it.  r=smaug
Bug 973849.  Allow clearInterval/clearTimeout calls with no arguments; just treat them as no-ops.  r=smaug