Improve 'Selection' exception messages.

LayoutTests/fast/dom/Selection/script-tests/collapseToX-empty-selection.js

 description("Test that collapseToStart() and collapseToEnd() throw INVALID_STATE_ERR if no selection is made.");
 
 var sel = window.getSelection();
 var textNode = document.createTextNode("abcdef");
 document.body.appendChild(textNode);
 
-shouldThrow("sel.collapseToStart()", "'InvalidStateError: An attempt was made to use an object that is not, or is no longer, usable.'");
-shouldThrow("sel.collapseToEnd()", "'InvalidStateError: An attempt was made to use an object that is not, or is no longer, usable.'");
+shouldThrow("sel.collapseToStart()");

[arv (Not doing code reviews), 2013/08/13 13:57:31]

Why don't you want to test the message any more?

[Mike West, 2013/08/13 14:00:17]

Laziness?

I realized that `shouldThrow` will output the message to the expectations file
if I leave the second parameter off entirely. That's a lot less work than
updating all the HTML files every time we iterated on some text. :)

[arv (Not doing code reviews), 2013/08/13 14:07:49]

I thought as much.

The problem is that we will end up with PASS even if the wrong exception is
thrown. It will require updating the expectation but as long as it says PASS I
doubt people will realize that they might have broken something.

(I really hate how we write our tests and this is one of the reasons.)

[Mike West, 2013/08/13 14:09:20]

That's a fair point. Hrm.

Ok. I'll attempt to overcome my laziness. :/

+shouldThrow("sel.collapseToEnd()");
 
 sel.selectAllChildren(textNode);
 
 shouldBe("sel.collapseToStart()", "undefined");
 shouldBe("sel.collapseToEnd()", "undefined");
 
 document.body.removeChild(textNode);