ES6: Implement WeakSet

ES6: Implement WeakSet

WeakSets work similar to ordinary Sets but the value (which must be an
object) is held weakly.

This is available under --harmony-collections

BUG=v8:2785
R=mstarzinger@chromium.org

Committed: http://code.google.com/p/v8/source/detail?r=15792

[arv (Not doing code reviews), 2013-07-19 01:08:53]

I introduced a shared super class, WeakCollection, and change the GC to only
operate on that.

Does this sound like a good approach?

[Michael Starzinger, 2013-07-19 09:50:20]

LGTM. Slam dunk. I'll wait for Andreas to take a brief look and then land this.

[rossberg, 2013-07-19 09:55:49]

https://codereview.chromium.org/19678023/diff/1/src/objects.h
File src/objects.h (right):

https://codereview.chromium.org/19678023/diff/1/src/objects.h#newcode67
src/objects.h:67: //           - WeakCollection
Just one nit: this should be named JSWeakCollection

[arv (Not doing code reviews), 2013-07-19 18:32:28]

On 2013/07/19 09:55:49, rossberg wrote:
> https://codereview.chromium.org/19678023/diff/1/src/objects.h
> File src/objects.h (right):
> 
> https://codereview.chromium.org/19678023/diff/1/src/objects.h#newcode67
> src/objects.h:67: //           - WeakCollection
> Just one nit: this should be named JSWeakCollection

PTAL

[Michael Starzinger, 2013-07-22 08:20:10]

Since Andreas is OOO this week, waiting for his reply doesn't make much sense.
His nit is addressed, so I'm landing this now.

[Michael Starzinger, 2013-07-22 08:21:43]

For the record, first version of this CL is at:
https://codereview.chromium.org/19429002/

[Michael Starzinger, 2013-07-22 08:32:40]

Committed patchset #5 manually as r15792 (presubmit successful).

[Michael Starzinger, 2013-07-22 08:34:24]

https://codereview.chromium.org/19678023/diff/11002/src/objects-printer.cc
File src/objects-printer.cc (right):

https://codereview.chromium.org/19678023/diff/11002/src/objects-printer.cc#ne...
src/objects-printer.cc:831: void JSWeakMap::JSWeakSetPrint(FILE* out) {
Typo s/JSWeakMap/JSWeakSet/ fixed while landing.