Throwing type check errors is very slow compared to other checks (e.g., value check error in typed …

Throwing type check errors is very slow compared to other checks (e.g., value check error in typed arrays). Take those checks out of the loop, whihc is there only to force optimization.
Committed: https://code.google.com/p/dart/source/detail?r=14503

[srdjan, 2012-11-02 22:16:03]

This fixes issue 6494

[regis, 2012-11-02 22:31:04]

LGTM