Stage ES2015-style const in sloppy mode

Stage ES2015-style const in sloppy mode

This patch switches sloppy-mode code from legacy const semantics
to ES2015 semantics. It is unknown how much of the web will be
broken by this; likely the patch will have to be reverted before
a branch happens.

BUG=v8:3739
LOG=Y
R=rossberg,adamk

Committed: https://crrev.com/0a0272dad09d35da2762baadc5b48c9d2b7f11ef
Cr-Commit-Position: refs/heads/master@{#31525}

[Dan Ehrenberg, 2015-10-23 11:17:53]

The CQ bit was checked by littledan@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-10-23 11:17:57]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1420223003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1420223003/1

[Dan Ehrenberg, 2015-10-23 11:18:22]

Description was changed from

==========
Stage ES2015-style const in sloppy mode

This patch switches sloppy-mode code from legacy const semantics
to ES2015 semantics. It is unknown how much of the web will be
broken by this; likley the patch will have to be reverted before
a branch happens.

BUG=v8:3739
LOG=Y
R=rossberg,adamk
==========

to

==========
Stage ES2015-style const in sloppy mode

This patch switches sloppy-mode code from legacy const semantics
to ES2015 semantics. It is unknown how much of the web will be
broken by this; likely the patch will have to be reverted before
a branch happens.

BUG=v8:3739
LOG=Y
R=rossberg,adamk
==========

[commit-bot: I haz the power, 2015-10-23 12:28:06]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-10-23 12:28:07]

Dry run: This issue passed the CQ dry run.

[rossberg, 2015-10-23 14:02:34]

lgtm

[rossberg, 2015-10-23 14:02:47]

The CQ bit was checked by rossberg@chromium.org

[commit-bot: I haz the power, 2015-10-23 14:02:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1420223003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1420223003/1

[commit-bot: I haz the power, 2015-10-23 14:04:32]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-23 14:05:00]

Patchset 1 (id:??) landed as
https://crrev.com/0a0272dad09d35da2762baadc5b48c9d2b7f11ef
Cr-Commit-Position: refs/heads/master@{#31525}