Inconsistent behavior between VM and Dart2JS

[gramster]

Consider the following program:

main() {
  bugbug(2.0);
}

bugbug(x) {
  print(x);
  List l = [ 0, 1, 2];
  print (l[x]);
}

With dart2js, we get:

2
2

In the VM, we get:

2.0
Exception: type 'double' is not a subtype of type 'int' of 'index'.

I'm guessing that the VM is right, so I'm putting this in the dart2js area, although I prefer the behavior of dart2js.

[peter-ahe-google]

Added Duplicate label.
Marked as being merged into #1533.