[Isolates] ScavengeVisitor gets member Heap*.

Improves splay.js by 7%.

Committed: http://code.google.com/p/v8/source/detail?r=5481

[Dmitry Titov, 2010-09-15 02:24:06]

No it doesn't improve splay.js, this test simply can give results in a wide
enough range.

Please don't bother to look at it :-)

[yurys, 2010-09-15 08:20:17]

LGTM

[Dmitry Titov, 2010-09-16 03:50:19]

Could you please take another look?

The change now actually improve splay.js (this is the test I've used for
profiling). Here are changes:

Page gets a new member in the header, "heap". This does not increase the size of
the header since it is 32-byte aligned (on ia32).

The ScavengeVisitor also gets a heap_ member.

Also StackLimitCheck gets an isolate_ member.

These changes mostly affect Heap::Scavenge() call tree, removing many instances
of Isolate::Current() from it.

[yurys, 2010-09-16 12:26:38]

LGTM

[Vitaly Repeshko, 2010-09-16 12:36:39]

LGTM with a few nits.

http://codereview.chromium.org/3382007/diff/4001/5002
File src/heap.cc (right):

http://codereview.chromium.org/3382007/diff/4001/5002#newcode819
src/heap.cc:819: ScavengeVisitor(Heap* heap) : heap_(heap) {}
nit: "explicit"

http://codereview.chromium.org/3382007/diff/4001/5002#newcode835
src/heap.cc:835: Heap* heap_;
nit: Insert a blank line before the field.

http://codereview.chromium.org/3382007/diff/4001/5003
File src/isolate.h (right):

http://codereview.chromium.org/3382007/diff/4001/5003#newcode1104
src/isolate.h:1104: StackLimitCheck(Isolate* isolate) : isolate_(isolate) { }
nit: "explicit"

http://codereview.chromium.org/3382007/diff/4001/5011
File src/spaces.h (right):

http://codereview.chromium.org/3382007/diff/4001/5011#newcode352
src/spaces.h:352: Heap* heap;
I know this class is already inconsistent in this regard, but this field should
be named "heap_".