Allow specifying base offset when constructing Keyed hydrogen instructions

Allow specifying base offset when constructing Keyed hydrogen instructions

This is preparation for pending hydrogen stub work that needs to access memory using KeyedLoad/KeyedStore operations where the base offset used for the accesses are is the the default (e.g. the size of an FixedArray header for FixedArrays or zero for external arrays).

R=mvstanton@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=21426

[danno, 2014-05-22 08:17:23]

PTAL

[mvstanton, 2014-05-22 08:32:21]

Looks very straightforward.
LGTM.

[danno, 2014-05-22 08:38:05]

Committed patchset #8 manually as r21426 (presubmit successful).