Revert "Use a pool to restrict access to file descriptors in pub."

Revert "Use a pool to restrict access to file descriptors in pub."

This reverts r30830. This revert is just a test to see whether this CL caused
the windows bots to start failing or if it was a coincidence.

R=rnystrom@google.com
TBR

Committed: https://code.google.com/p/dart/source/detail?r=30837

[nweiz, 2013-12-04 00:33:49]

Committed patchset #1 manually as r30837 (presubmit successful).

[Bob Nystrom, 2013-12-04 00:58:45]

lgtm