Remove obsolete JSFunction::IsOptimizable predicate.

Remove obsolete JSFunction::IsOptimizable predicate.

This just delegates to SharedFunctionInfo::optimization_disabled and
was primarily used for assertions. Removing it due to misleading name
because already optimized functions reported being "non-optimizable".

R=titzer@chromium.org

Committed: https://crrev.com/181d7b85977eb752b19e1de902093783e31330ef
Cr-Commit-Position: refs/heads/master@{#28551}

[Benedikt Meurer, 2015-05-21 11:28:10]

bmeurer@chromium.org changed reviewers:
+ bmeurer@chromium.org

[Benedikt Meurer, 2015-05-21 11:28:10]

lgtm

[Michael Starzinger, 2015-05-21 13:04:04]

The CQ bit was checked by mstarzinger@chromium.org

[commit-bot: I haz the power, 2015-05-21 13:04:15]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1150683002/1

[commit-bot: I haz the power, 2015-05-21 13:05:55]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-21 13:06:04]

Patchset 1 (id:??) landed as
https://crrev.com/181d7b85977eb752b19e1de902093783e31330ef
Cr-Commit-Position: refs/heads/master@{#28551}

[Michael Starzinger, 2015-05-21 13:34:32]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/1148973005/ by mstarzinger@chromium.org.

The reason for reverting is: Causes assertions to fire when serializing
optimized code..