Testing constructors with no arguments misses some ways of disabling constructors

[foolip]

mdn/browser-compat-data#7923 revealed that there's a problem with our generated tests for the Notification constructor, which testing new Notification('hello') (and expecting that to work) would have avoided.

The problem is that we're probing for error messages thrown by generated bindings for anything that has a Web IDL constructor, but it's also possible to disable constructors by throwing exceptions from non-generated code.

We could add "Illegal constructor" to the list of strings that we check for, but the general problem can only be solved by invoking the constructor in a way that should work, and only treating it as supported if it does. Unfortunately this would be a lot of work...

[foolip]

Here's the code:

mdn-bcd-collector/static/resources/harness.js

Lines 113 to 145 in 213350e

	function testConstructor(iface) {
	var result = {};
	try {
	eval('new '+iface+'()');
	result.result = true;
	} catch (err) {
	if (
	stringIncludes(err.message, 'Illegal constructor') ||
	stringIncludes(err.message, 'is not a constructor') ||
	stringIncludes(err.message, 'Function expected')
	) {
	result.result = false;
	} else if (
	stringIncludes(err.message, 'Not enough arguments') ||
	stringIncludes(err.message, 'argument required') ||
	stringIncludes(err.message, 'arguments required') ||
	stringIncludes(err.message, 'Argument not optional') ||
	stringIncludes(err.message, 'Arguments can\'t be empty') ||
	stringIncludes(err.message, 'undefined is not an object')
	) {
	// If it failed to construct and it's not illegal or just needs
	// more arguments, the constructor's good
	result.result = true;
	} else {
	result.result = null;
	}
	result.message = 'threw ' + stringify(err);
	}
	return result;
	}

We already check for "Illegal constructor" but that doesn't help if we invoke the constructor with too few arguments.