Implement List<T> operations on dom types via manual mixins.

Implement List<T> operations on dom types via manual mixins.

This gets HTMLCollectionTest.html and Typing.html from the layout
tests working for Frog.

I tried using a hidden native parameterized base class but that did
not work, so I had to backed off to having to mix-in the
List<T> methods on each native class that implements List<T>.
This is what we did with dartc.

The mixins are in a template - not quite as bad as in the python code
but still not so easy for others to find.

BUG=
TEST=

Committed: https://code.google.com/p/dart/source/detail?r=3590