Add a hash map for a raw object to id mapping, this table will be used during snapshot writing in o…

Add a hash map for a raw object to id mapping, this table will be used during snapshot writing in order to map a raw object to an object id. This would enable us to get rid of the current scheme of displacing the object header with the object id while writing a snapshot (requires no GC should be happening while a snapshot is being written and hampers concurrent GC).

R=iposva@google.com

Committed: https://github.com/dart-lang/sdk/commit/98cdaecda2d544a9090566d29152f0ee0a59a072

[siva, 2015-10-09 17:08:38]

asiva@google.com changed reviewers:
+ iposva@google.com

[Ivan Posva, 2015-10-12 09:19:00]

LGTM -ip

https://codereview.chromium.org/1399783002/diff/20001/runtime/vm/heap.cc
File runtime/vm/heap.cc (right):

https://codereview.chromium.org/1399783002/diff/20001/runtime/vm/heap.cc#newc...
runtime/vm/heap.cc:651: new_weak_tables_[kHashes]->count() +
old_weak_tables_[kHashes]->count();
The line wrapping below is much nicer than this. Do you mind updating it here as
well?

[siva, 2015-10-12 17:50:19]

https://codereview.chromium.org/1399783002/diff/20001/runtime/vm/heap.cc
File runtime/vm/heap.cc (right):

https://codereview.chromium.org/1399783002/diff/20001/runtime/vm/heap.cc#newc...
runtime/vm/heap.cc:651: new_weak_tables_[kHashes]->count() +
old_weak_tables_[kHashes]->count();
On 2015/10/12 09:19:00, Ivan Posva wrote:
> The line wrapping below is much nicer than this. Do you mind updating it here
as
> well?

Done.

[siva, 2015-10-12 18:05:58]

Committed patchset #3 (id:40001) manually as
98cdaecda2d544a9090566d29152f0ee0a59a072 (presubmit successful).