Fix HIsSmiAndBranch::KnownSuccessorBlock() by deleting it

Fix HIsSmiAndBranch::KnownSuccessorBlock() by deleting it

Constants can still change their representation, so we cannot determine reachability of blocks based on their Smi-ness

BUG=chromium:351320
LOG=y
R=yangguo@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=19836

[Jakob Kummerow, 2014-03-12 10:05:28]

PTAL.

There are other options we could consider, such as updating HIsSmiAndBranch's
RequiredInputRepresentation after deciding for a known successor. But I'd prefer
to land this easy, safe fix first, and punt on any more advanced hackery.

[Yang, 2014-03-12 10:10:29]

lgtm

[Jakob Kummerow, 2014-03-12 10:14:38]

Committed patchset #1 manually as r19836 (tree was closed).