[parser] only parse async arrow function when necessary

[parser] only parse async arrow function when necessary

Previously, an async arrow function would be parsed if any valid
ConditionalExpression began with the identifier "async", and its following token
was on the same line.

So for example, `async.bar foo => 1` was parsed as a valid async arrow function.
This patch corrects this behaviour by asserting that the following token is a
valid arrow parameters start.

BUG=v8:4483
R=littledan@chromium.org, henrique.ferreiro@gmail.com

Committed: https://crrev.com/e45fba811fbf15751c3464c0d3973f6f8ee5c934
Cr-Commit-Position: refs/heads/master@{#37154}

[caitp (gmail), 2016-06-21 19:04:58]

Hey, PTAL guys.

[caitp (gmail), 2016-06-21 19:05:23]

Description was changed from

==========
[parser] only parse async arrow function when necessary

Previously, an async arrow function would be parsed if any valid
ConditionalExpression began with the identifier "async", and its following token
was on the same line.

So for example, `async.bar => 1` was parsed as a valid async arrow function.
This patch corrects this behaviour by asserting that the following token is a
valid arrow parameters start.

BUG=v8:4483
R=littledan@chromium.org, henrique.ferreiro@gmail.com
==========

to

==========
[parser] only parse async arrow function when necessary

Previously, an async arrow function would be parsed if any valid
ConditionalExpression began with the identifier "async", and its following token
was on the same line.

So for example, `async.bar foo => 1` was parsed as a valid async arrow function.
This patch corrects this behaviour by asserting that the following token is a
valid arrow parameters start.

BUG=v8:4483
R=littledan@chromium.org, henrique.ferreiro@gmail.com
==========

[Dan Ehrenberg, 2016-06-21 19:16:47]

lgtm

[caitp (gmail), 2016-06-21 19:21:23]

The CQ bit was checked by caitpotter88@gmail.com

[commit-bot: I haz the power, 2016-06-21 19:21:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2089733002/1

[commit-bot: I haz the power, 2016-06-21 19:46:47]

Description was changed from

==========
[parser] only parse async arrow function when necessary

Previously, an async arrow function would be parsed if any valid
ConditionalExpression began with the identifier "async", and its following token
was on the same line.

So for example, `async.bar foo => 1` was parsed as a valid async arrow function.
This patch corrects this behaviour by asserting that the following token is a
valid arrow parameters start.

BUG=v8:4483
R=littledan@chromium.org, henrique.ferreiro@gmail.com
==========

to

==========
[parser] only parse async arrow function when necessary

Previously, an async arrow function would be parsed if any valid
ConditionalExpression began with the identifier "async", and its following token
was on the same line.

So for example, `async.bar foo => 1` was parsed as a valid async arrow function.
This patch corrects this behaviour by asserting that the following token is a
valid arrow parameters start.

BUG=v8:4483
R=littledan@chromium.org, henrique.ferreiro@gmail.com
==========

[commit-bot: I haz the power, 2016-06-21 19:46:49]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-06-21 19:48:24]

Description was changed from

==========
[parser] only parse async arrow function when necessary

Previously, an async arrow function would be parsed if any valid
ConditionalExpression began with the identifier "async", and its following token
was on the same line.

So for example, `async.bar foo => 1` was parsed as a valid async arrow function.
This patch corrects this behaviour by asserting that the following token is a
valid arrow parameters start.

BUG=v8:4483
R=littledan@chromium.org, henrique.ferreiro@gmail.com
==========

to

==========
[parser] only parse async arrow function when necessary

Previously, an async arrow function would be parsed if any valid
ConditionalExpression began with the identifier "async", and its following token
was on the same line.

So for example, `async.bar foo => 1` was parsed as a valid async arrow function.
This patch corrects this behaviour by asserting that the following token is a
valid arrow parameters start.

BUG=v8:4483
R=littledan@chromium.org, henrique.ferreiro@gmail.com

Committed: https://crrev.com/e45fba811fbf15751c3464c0d3973f6f8ee5c934
Cr-Commit-Position: refs/heads/master@{#37154}
==========

[commit-bot: I haz the power, 2016-06-21 19:48:26]

Patchset 1 (id:??) landed as
https://crrev.com/e45fba811fbf15751c3464c0d3973f6f8ee5c934
Cr-Commit-Position: refs/heads/master@{#37154}