Destructuring array without initializer throws an exception

Destructuring array without initializer throws an exception

Previously, cases like
  var [foo]
led to a parser crash because the parser tried to do something with
the initializer, which was not syntactically present.

This patch fixes the parser issue (implicitly creating an undefined
initializer) and inserts a check for array destructuring that the
right-hand side is coercible to an object, so it can have iterator
methods called on it safely.

BUG=v8:4462
LOG=Y
R=adamk

Committed: https://crrev.com/2e7077e02c2aacda5bc349b415b46dbb9e2f1a34
Cr-Commit-Position: refs/heads/master@{#31128}

[Dan Ehrenberg, 2015-10-06 00:11:36]

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

[commit-bot: I haz the power, 2015-10-06 00:11:47]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1384413002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1384413002/1

[commit-bot: I haz the power, 2015-10-06 00:37:29]

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

[commit-bot: I haz the power, 2015-10-06 00:37:30]

Dry run: This issue passed the CQ dry run.

[adamk, 2015-10-06 16:59:47]

The CQ bit was checked by adamk@chromium.org

[adamk, 2015-10-06 16:59:47]

lgtm

[commit-bot: I haz the power, 2015-10-06 17:00:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1384413002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1384413002/1

[commit-bot: I haz the power, 2015-10-06 17:01:15]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-06 17:01:39]

Patchset 1 (id:??) landed as
https://crrev.com/2e7077e02c2aacda5bc349b415b46dbb9e2f1a34
Cr-Commit-Position: refs/heads/master@{#31128}