Fix reuse of free blocks and delete global cache on VM shutdown.

Fix reuse of free store buffer blocks from the global cache of free blocks.

Add StoreBuffer::ShutDown to delete global cache of free blocks on VM shutdown.

BUG=https://github.com/dart-lang/sdk/issues/24129
R=iposva@google.com

Committed: https://github.com/dart-lang/sdk/commit/74e02785b0e534e469668ce2cabced7d26ec55b1

[koda, 2015-08-21 03:21:33]

koda@google.com changed reviewers:
+ iposva@google.com, zra@google.com

[koda, 2015-08-21 03:21:33]

Note that we are already limiting the max size of this list, so it cannot
explain any large leaks, but at least this will silence some ASAN warnings
around shutdown (and that's how I found it).

[Ivan Posva, 2015-08-21 03:27:12]

LGTM -ip

[koda, 2015-08-21 13:18:27]

Patchset #2 (id:20001) has been deleted

[koda, 2015-08-21 13:29:08]

Found a more serious issue: the empty blocks were not actually being reused due
to a missing "return".
Updated this CL.

PTAL

[Cutch, 2015-08-21 13:36:36]

On 2015/08/21 13:29:08, koda wrote:
> Found a more serious issue: the empty blocks were not actually being reused
due
> to a missing "return".
> Updated this CL.
> 
> PTAL

Good catch!

[koda, 2015-08-21 14:20:27]

On 2015/08/21 13:36:36, Cutch wrote:
> On 2015/08/21 13:29:08, koda wrote:
> > Found a more serious issue: the empty blocks were not actually being reused
> due
> > to a missing "return".
> > Updated this CL.
> > 
> > PTAL
> 
> Good catch!

Note that this more serious issue could potentially leak 8KB for every new-space
GC, without any bound.

[koda, 2015-08-21 15:37:14]

Committed patchset #3 (id:60001) manually as
74e02785b0e534e469668ce2cabced7d26ec55b1 (presubmit successful).