Add a flag to track detached contexts.

Add a flag to track detached contexts.

When embedder detaches the global objects, its context must be garbage
collected eventually.

BUG=

Committed: https://crrev.com/b7d27ea58307e9201c1196cf2cf523205cd8ab60
Cr-Commit-Position: refs/heads/master@{#26450}

[ulan, 2015-02-04 15:39:04]

ulan@chromium.org changed reviewers:
+ jochen@chromium.org

[ulan, 2015-02-04 15:39:05]

PTAL

https://codereview.chromium.org/898663005/diff/1/src/isolate.cc
File src/isolate.cc (right):

https://codereview.chromium.org/898663005/diff/1/src/isolate.cc#newcode2607
src/isolate.cc:2607: static_cast<void*>(cell->value()), mark_sweeps);
Would be nice to print the retaining path for the context. I'll add that in
future CL after implementing better path tracer in GC.

[jochen (gone - plz use gerrit), 2015-02-04 17:09:04]

lgtm

[ulan, 2015-02-04 17:11:03]

New patchsets have been uploaded after l-g-t-m from jochen@chromium.org

[ulan, 2015-02-05 09:12:14]

The CQ bit was checked by ulan@chromium.org

[ulan, 2015-02-05 09:12:20]

The CQ bit was checked by ulan@chromium.org

[commit-bot: I haz the power, 2015-02-05 09:12:38]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/898663005/60001

[commit-bot: I haz the power, 2015-02-05 09:35:55]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2015-02-05 09:36:08]

Patchset 4 (id:??) landed as
https://crrev.com/b7d27ea58307e9201c1196cf2cf523205cd8ab60
Cr-Commit-Position: refs/heads/master@{#26450}