Be lazier when capturing stack traces.

Be lazier when capturing stack traces.

It turns out that capturing stack traces is cheap; converting them to strings is
what's so expensive.

R=rnystrom@google.com

Committed: https://code.google.com/p/dart/source/detail?r=22205

[Bob Nystrom, 2013-04-30 21:15:05]

LGTM.

Do you plan to remove the code from pub/scheduled_test that disables stack trace
collection? If so, can you make sure to do some before/after times on running
all of the pubtests just to make sure it's still fast?

[nweiz, 2013-04-30 21:25:43]

On 2013/04/30 21:15:05, Bob Nystrom wrote:
> Do you plan to remove the code from pub/scheduled_test that disables stack
trace
> collection? If so, can you make sure to do some before/after times on running
> all of the pubtests just to make sure it's still fast?

Yeah, I was planning on doing that contingent on making sure it was still fast.

[nweiz, 2013-04-30 21:34:13]

Committed patchset #1 manually as r22205 (presubmit successful).