[es6] Remove left-overs from Function.prototype.toMethod.

[es6] Remove left-overs from Function.prototype.toMethod.

The actual Function.prototype.toMethod was removed some time already,
but there were some stuff (esp. %ToMethod) left in the tree, including
tests for %ToMethod.  This code (and esp. the tests) cause trouble in
the process of moving bound functions away from JSFunction; so since
the code is unused anyway, we can as well remove it.

The original removal of Function.prototype.toMethod was in February
2015 in 68e489758607bb7373409b49a0a7883407a322b3.

R=jarin@chromium.org
BUG=v8:3330
LOG=n

Committed: https://crrev.com/ff2c9eace4cd987de3efcfdddc92143ede5d2c76
Cr-Commit-Position: refs/heads/master@{#30925}

[Benedikt Meurer, 2015-09-25 03:42:42]

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

[Benedikt Meurer, 2015-09-25 03:42:43]

Dead code must be dead!

[Jarin, 2015-09-25 04:02:01]

lgtm

[Benedikt Meurer, 2015-09-25 04:02:19]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2015-09-25 04:02:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1366063002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1366063002/1

[commit-bot: I haz the power, 2015-09-25 04:04:34]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-25 04:04:45]

Patchset 1 (id:??) landed as
https://crrev.com/ff2c9eace4cd987de3efcfdddc92143ede5d2c76
Cr-Commit-Position: refs/heads/master@{#30925}