Adds logic to bump up the default heap for invoking dartc on Mac.

Adds logic to bump up the default heap for invoking dartc on Mac.

[zundel, 2011-11-22 13:30:46]

See issue 173:  http://code.google.com/p/dart/issues/detail?id=173

[ahe, 2011-11-22 13:33:35]

I thought we were getting rid of the --optimize option?

http://codereview.chromium.org/8613007/diff/2001/compiler/java/com/google/dar...
File compiler/java/com/google/dart/compiler/UnitTestBatchRunner.java (right):

http://codereview.chromium.org/8613007/diff/2001/compiler/java/com/google/dar...
compiler/java/com/google/dart/compiler/UnitTestBatchRunner.java:53: System.gc();
Does this have any impact on performance?

[zundel, 2011-11-28 20:30:13]

Srdjan ran some tests on Mac experimenting with heap size:

./tools/test.py --component dartc
co19/LangSpecTest/13_Types/13_4_Interface_Types/A11/t01 

-Xmx128m crashes, -Xmx180m passes

This is after submitting http://codereview.chromium.org/8698021/ to reduce
memory usage.

Would this patch be more appealing if I reduced the heap size increase to 512 or
256M?

[ahe, 2011-11-28 21:06:59]

I'd rather skip the problematic test and record it as a known issue. Last time
we bumped up the memory, it turned out to be a memory leak instead. I'm worried
that increasing the memory limit could hide future memory issues.

However, dartc is not my responsibility. This is only meant as advice. I have
removed myself as reviewer to make it clear that I do not want to prevent you
from doing what you think is best.

[zundel, 2011-11-29 16:57:12]

The running out of memory did turn out to be an architecture issue in Dartc.  We
didn't see it before because this test wasn't introduced until Oct31 and
possibly not integrated into the Dart build until sometime after that. I guess
no one ran all the tests on a mac until recently. 

I addressed the root cause in another change.  Taking the discussion in this
thread into account, I decided in this other CL to constrain heap for unit
testing to 128M on all platforms, and propose bumping up the memory for regular
dartc invocations to 256M.

closing this issue in favor of:
http://codereview.chromium.org/8659022/