Do the right thing when setPrototypeOf is impossible to shim.
Improve test suite for Promise.

A number of the asynchronous tests were timing out after uncaught
exceptions rather than properly reporting thrown exceptions.
WIP: Test chrome.
XXX CHROME DEBUG XXX
Use latest es5-shim.
Promise.all debugging
XXX Chop down set of browsers tested.
skip all but one Promise.all tests
more promise debugging