Increment descriptor array slack for prototypes by a constant rather than 50%

Increment descriptor array slack for prototypes by a constant rather than 50%
Additionally speed up instantiation of ObjectTemplates by preallocating enough space in the descriptor arrays

BUG=v8:4184
LOG=n

Committed: https://crrev.com/b0493ed16c0b363a0e92bf4a790d4fd851c74e70
Cr-Commit-Position: refs/heads/master@{#29468}

[Toon Verwaest, 2015-07-03 11:41:45]

verwaest@chromium.org changed reviewers:
+ ishell@chromium.org

[Toon Verwaest, 2015-07-03 11:41:45]

ptal

Should probably first create the map and afterwards the instance in
api-natives.cc, but this will do for now.

[Igor Sheludko, 2015-07-03 13:56:40]

lgtm with a nit and suggestion:

https://codereview.chromium.org/1218403002/diff/1/src/api-natives.cc
File src/api-natives.cc (right):

https://codereview.chromium.org/1218403002/diff/1/src/api-natives.cc#newcode150
src/api-natives.cc:150: PropertyKind kind = length == 3 ? kData : kAccessor;
Instead of writing a length we could pack kind and attributes into
PropertyDetails to save one word per property.

https://codereview.chromium.org/1218403002/diff/1/src/api-natives.cc#newcode157
src/api-natives.cc:157: if (TransitionArray::SearchTransition(obj->map(), kind,
*name,
Put this call after all the simple checks.

[Igor Sheludko, 2015-07-03 13:56:41]

lgtm with a nit and suggestion:

[Toon Verwaest, 2015-07-03 14:29:05]

Addressed comments

[Igor Sheludko, 2015-07-03 14:35:56]

lgtm

[Toon Verwaest, 2015-07-03 14:41:42]

The CQ bit was checked by verwaest@chromium.org

[commit-bot: I haz the power, 2015-07-03 14:41:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1218403002/40001

[commit-bot: I haz the power, 2015-07-03 15:06:46]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-07-03 15:07:00]

Patchset 3 (id:??) landed as
https://crrev.com/b0493ed16c0b363a0e92bf4a790d4fd851c74e70
Cr-Commit-Position: refs/heads/master@{#29468}