Drop obsolete HCheckMaps::HandleSideEffectsDominator().

Drop obsolete HCheckMaps::HandleSideEffectsDominator().

In HCheckMaps::HandleSideEffectsDominator() we try to remove
redundant HCheckMaps instructions that are dominated by an
HStoreNamedField instruction with a transition. This is just
a special case of the check elimination and therefore obsolete
(it also gives some nice speedup since GVN just got cheaper).

R=svenpanne@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=21108

[Benedikt Meurer, 2014-05-01 11:28:51]

Because fast! :-)

[Sven Panne, 2014-05-02 05:53:49]

lgtm

[Benedikt Meurer, 2014-05-02 05:59:13]

Committed patchset #1 manually as r21108 (presubmit successful).