Fix ImageData constructor infelicity.

Fix ImageData constructor infelicity.

Correctly handle the optional third argument for the overload

 ImageData(Uint8ClampedArray d, unsigned long w, optional unsigned long h)

It should not throw if not supplied, but should throw if supplied and zero.

Also, delegate the object interface typecheck to generated bindings code.

R=junov
BUG=338804
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=188847

[sof, 2015-01-22 20:25:50]

sigbjornf@opera.com changed reviewers:
+ haraken@chromium.org, junov@chromium.org

[sof, 2015-01-22 20:25:50]

Please take a look.

[Justin Novosad, 2015-01-22 20:58:21]

On 2015/01/22 20:25:50, sof wrote:
> Please take a look.

lgtm

[sof, 2015-01-22 21:02:43]

The CQ bit was checked by sigbjornf@opera.com

[commit-bot: I haz the power, 2015-01-22 21:03:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/871563003/1

[haraken, 2015-01-23 01:20:44]

LGTM

[commit-bot: I haz the power, 2015-01-23 02:36:22]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=188847