Another fix for non-mac build:

Another fix for non-mac build:

../runtime/platform/assert.h: In member function ‘void dart::DynamicAssertionHelper::Equals(const E&, const A&) [with E = int, A = uint64_t]’:
../runtime/vm/thread_pool_test.cc:64:   instantiated from here
../runtime/platform/assert.h:98: error: comparison between signed and unsigned integer expressions
Committed: https://code.google.com/p/dart/source/detail?r=5486

[turnidge, 2012-03-14 21:10:04]

TBR=iposva

[Ivan Posva, 2012-03-15 00:43:15]

Please see the comment in the original thread pool change. But this change
should not have been needed, if I had paid better attention during your review.

-Ivan