Introduce object visitor to estimate the size of a native context.

Introduce object visitor to estimate the size of a native context.

This is only an estimate since it counts objects that could be shared,
for example strings, cow arrays, heap numbers, etc.

It however ignores objects that could be shared, but may only be used
by the context to be measured, for example shared function infos,
script objects, scope infos, etc.

R=jochen@chromium.org

Committed: https://crrev.com/0a1a714f7e700b3d882e3485008fa5a24cf80584
Cr-Commit-Position: refs/heads/master@{#30029}

[jochen (gone - plz use gerrit), 2015-08-05 11:39:46]

lgtm, thx

https://codereview.chromium.org/1268333004/diff/1/src/api.cc
File src/api.cc (right):

https://codereview.chromium.org/1268333004/diff/1/src/api.cc#newcode395
src/api.cc:395: 
nit. remove

https://codereview.chromium.org/1268333004/diff/1/src/bootstrapper.cc
File src/bootstrapper.cc (right):

https://codereview.chromium.org/1268333004/diff/1/src/bootstrapper.cc#newcode...
src/bootstrapper.cc:2411: ObjectHashTable::New(isolate(),
ApiNatives::kInitialFunctionCacheSize);
unrelated?

[jochen (gone - plz use gerrit), 2015-08-05 11:40:28]

actually, could you also add a getter to v8::Context in include/v8.h so we could
use this from blink?

[Yang, 2015-08-05 12:02:10]

Addressed comments. Another look?

[Yang, 2015-08-05 12:03:07]

The CQ bit was checked by yangguo@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-08-05 12:03:18]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1268333004/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1268333004/20001

[commit-bot: I haz the power, 2015-08-05 12:35:05]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-05 12:35:06]

Dry run: This issue passed the CQ dry run.

[Yang, 2015-08-05 12:53:42]

The CQ bit was checked by yangguo@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-08-05 12:53:51]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1268333004/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1268333004/40001

[commit-bot: I haz the power, 2015-08-05 13:02:05]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-05 13:02:06]

Dry run: Try jobs failed on following builders:
  v8_win_rel on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_win_rel/builds/8391)

[Yang, 2015-08-05 13:32:58]

The CQ bit was checked by yangguo@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-08-05 13:33:07]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1268333004/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1268333004/60001

[commit-bot: I haz the power, 2015-08-05 13:59:08]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-05 13:59:09]

Dry run: This issue passed the CQ dry run.

[Yang, 2015-08-05 14:04:16]

On 2015/08/05 13:59:09, commit-bot: I haz the power wrote:
> Dry run: This issue passed the CQ dry run.

Jochen, another look? Also, you can CQ if it looks good.

[jochen (gone - plz use gerrit), 2015-08-05 14:04:55]

The CQ bit was checked by jochen@chromium.org

[jochen (gone - plz use gerrit), 2015-08-05 14:04:56]

lgtm

[commit-bot: I haz the power, 2015-08-05 14:05:00]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1268333004/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1268333004/60001

[commit-bot: I haz the power, 2015-08-05 14:07:23]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2015-08-05 14:07:56]

Patchset 4 (id:??) landed as
https://crrev.com/0a1a714f7e700b3d882e3485008fa5a24cf80584
Cr-Commit-Position: refs/heads/master@{#30029}