[runtime] Remove premature optimization from ToPrimitive.

[runtime] Remove premature optimization from ToPrimitive.

The !IS_SPEC_OBJECT(x) check implies both IS_STRING(x) and
IS_SIMD_VALUE(x), and generates shorter/better code.  So we
can safely remove the redundant checks.

R=rossberg@chromium.org

Committed: https://crrev.com/0c674828dc2bdefd6f111d278408a938686edcfd
Cr-Commit-Position: refs/heads/master@{#30081}

[Benedikt Meurer, 2015-08-08 18:46:53]

Hey Andreas,

Here's an easy one that I discovered while looking into how we can fix
ToPrimitive to be ES6 compliant.
Please take a look.

Thanks,
Benedikt

[Jarin, 2015-08-10 05:27:01]

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

[Jarin, 2015-08-10 05:27:02]

lgtm

[Benedikt Meurer, 2015-08-10 05:27:08]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2015-08-10 05:27:15]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1278873007/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1278873007/1

[commit-bot: I haz the power, 2015-08-10 06:07:25]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-10 06:07:44]

Patchset 1 (id:??) landed as
https://crrev.com/0c674828dc2bdefd6f111d278408a938686edcfd
Cr-Commit-Position: refs/heads/master@{#30081}