avm2: Implement XMLList.contains

[Lord-McSweeney]

No description provided.

[sleepycatcoding]

This does not seem to be entirely correct.

var x = new XMLList("<item>A</item><item>B</item>");
var x1 = new XMLList("<item>A</item>");

trace(x.contains("A")); // False with this PR, true in Flash
trace(x.contains("B")); // False with this PR, true in Flash

trace(x.contains(x));
trace(x.contains(x1));

trace(x.contains(new XML("<item>A</item>")));

[kmeisthax]

@sleepycatcoding On xml_list.rs line 221 it specifically returns false if the XMLList holds more than one node - i.e. multiple nodes in an XMLList isn't implemented yet.

[sleepycatcoding]

@sleepycatcoding On xml_list.rs line 221 it specifically returns false if the XMLList holds more than one node - i.e. multiple nodes in an XMLList isn't implemented yet.

Yeah, I know, this was just some code I wrote for testing and I copied all of it into the comment 😅, I more meant that x.contains("A") did not work as expected.

[Lord-McSweeney]

On xml_list.rs line 221 it specifically returns false if the XMLList holds more than one node - i.e. multiple nodes in an XMLList isn't implemented yet.

@kmeisthax This seemed to match FP from my testings, .contains([some multi-node XMLList]) will always return false.

[Lord-McSweeney]

Superseded by #16525.