Use DescriptorArray when checking if an object has a property

Use DescriptorArray when checking if an object has a property

DescriptorArray provides a faster idea of if an object has a property. Use it for JSReceiver::HasProperty & JSObject::HasRealNamedProperty.

BUG=v8:2472
LOG=N

[hichris123, 2015-08-24 02:16:56]

hichris123@gmail.com changed reviewers:
+ verwaest@chromium.org

[hichris123, 2015-08-24 02:18:12]

hichris123@gmail.com changed reviewers:
+ danno@chromium.org

[hichris123, 2015-08-24 02:22:30]

verwaest@/danno@: PTAL. This should speed up `"y" in x` and
`x.hasOwnProperty("y")`.

One thing is I haven't figured out why, but the LookupIterator is still needed
if a property isn't found in the DescriptorArray(s). This slows down cases where
the property doesn't exist, as it has to search over the DescriptorArray and
then use the LookupIterator. Any ideas on that?

[Toon Verwaest, 2015-10-02 08:17:56]

Does not lgtm, exactly since it skips all the work that is required to do a
correct (and secure) lookup. The LookupIterator does exactly the work that is
necessary, not more.

That's not to say there are no other optimizations possible. We already have
those on our roadmap though.

[hichris123, 2015-10-02 14:50:57]

On 2015/10/02 08:17:56, Toon Verwaest wrote:
> Does not lgtm, exactly since it skips all the work that is required to do a
> correct (and secure) lookup. The LookupIterator does exactly the work that is
> necessary, not more.
> 
> That's not to say there are no other optimizations possible. We already have
> those on our roadmap though.

Ah yeah, I probably should've closed this review earlier. I was looking into
better options... and I kinda forgot about this CL.