Fix flaky test runtime/vm/heap_profiler_test.cc

Fix flaky test runtime/vm/heap_profiler_test.cc


BUG=3634
TEST=vm/heap_profiler_test

Committed: https://code.google.com/p/dart/source/detail?r=8648

[Bill Hesse, 2012-06-14 11:35:22]

The >= and <= checks were reversed.  The test was flaky because the values are
usually equal (the time in milliseconds), so it passed when they were equal.

[Mads Ager (google), 2012-06-14 11:43:02]

lgtm

[cshapiro, 2012-06-14 19:21:07]

lgtm, too

thanks