IDL: Null values should be converted for non-nullable dictionary members (re-land)

IDL: Null values should be converted for non-nullable dictionary members (re-land)

This is the second attempt to land reverted CL (https://codereview.chromium.org/765673005/)
with GN fix.

Original description:

The current implementation of the binding layer treats null values
as the same as undefined, but this behavior doesn't match what the
spec specified. According to the spec[1], when null is passed to
a dictionary member, we should do conversion unless the member is
nullable. For example, given a dictionary member and the type
of the member is DOMString, passing null should result in "null"
(of type string). This CL changes the binding's behavior to follow
the spec.

[1] http://heycam.github.io/webidl/#es-dictionary
BUG=321462
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=186276

[bashi, 2014-12-02 00:04:10]

bashi@chromium.org changed reviewers:
+ haraken@chromium.org

[bashi, 2014-12-02 00:04:10]

PTAL? The only diff from the reverted CL is templates.gni.

[haraken, 2014-12-02 01:02:09]

LGTM

[bashi, 2014-12-02 01:02:30]

The CQ bit was checked by bashi@chromium.org

[commit-bot: I haz the power, 2014-12-02 01:03:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/771813002/1

[commit-bot: I haz the power, 2014-12-02 03:04:26]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=186276