Cleanup following MicrotaskQueue abstraction

https://code.google.com/p/v8/source/detail?r=19344 failed to remove the promiseEvents InternalArray.

R=rossberg@chromium.org, rossberg
LOG=N

Review URL: https://codereview.chromium.org/203773006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20092 ce2b1a6d-e550-0410-aec6-3dcde31c8c00