Allocate error messages in old space: needed for background compilation and rarely done

Allocate error messages in old space: needed for background compilation and rarely done

BUG=
R=koda@google.com, regis@google.com

Committed: https://github.com/dart-lang/sdk/commit/1a11dbfc1cad85683d4532c5cf2b95161d483ddd

[srdjan, 2015-10-01 15:51:22]

srdjan@google.com changed reviewers:
+ regis@google.com

[regis, 2015-10-01 15:58:46]

lgtm

[koda, 2015-10-01 16:15:41]

koda@google.com changed reviewers:
+ koda@google.com

[koda, 2015-10-01 16:15:42]

lgtm

Please add comments in the code about *why* they are allocated in old space, to
help future readers and prevent them from reverting this. (More generally, we
could consider having a scope in debug mode that asserts no new space
allocation.)

[srdjan, 2015-10-01 20:05:45]

On 2015/10/01 16:15:42, koda wrote:
> lgtm
> 
> Please add comments in the code about *why* they are allocated in old space,
to
> help future readers and prevent them from reverting this. (More generally, we
> could consider having a scope in debug mode that asserts no new space
> allocation.)

Added comments. Currently I have a temporary 'optimizing' flag to catch all
issues. With background compilation we need the suggested debug mode check.

[srdjan, 2015-10-01 20:13:18]

Committed patchset #3 (id:40001) manually as
1a11dbfc1cad85683d4532c5cf2b95161d483ddd (presubmit successful).