This reverts commit 0ade0386aa4168b48234bc7f33d30a62140b95ea.

Reason for revert:
Unexpected Failures:
* bindings/sequence-type.html
* custom-elements/spec/define-element.html
* external/wpt/custom-elements/CustomElementRegistry.html

on
https://ci.chromium.org/buildbot/chromium.webkit/WebKit%20Mac10.11%20%28dbg%29/
https://ci.chromium.org/buildbot/chromium.webkit/WebKit%20Linux%20Trusty%20%28dbg%29/

Speculatively reverting this to see if it's the cause.

Original change's description:
> Web Animations: Fix bugs in procedure to process a keyframes argument
>
> There were three minor bugs left in the implementation:
>
>   - We threw on lists-in-custom-iterators instead of just ignoring them.
>   - We returned all properties on the keyframe rather than just those
>     defined on the keyframe itself (e.g. we would include prototype
>     properties, against spec).
>   - We didn't access the properties in ascending unicode order.
>
> Bug: 827573
> Change-Id: I213ae5b24e1f35d7f28d16625025122950a6ba88
> Reviewed-on: https://chromium-review.googlesource.com/989261
> Reviewed-by: Kentaro Hara <haraken@chromium.org>
> Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
> Reviewed-by: Robert Flack <flackr@chromium.org>
> Commit-Queue: Stephen McGruer <smcgruer@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#550641}

TBR=flackr@chromium.org,yukishiino@chromium.org,jbroman@chromium.org,haraken@chromium.org,smcgruer@chromium.org

Change-Id: I5e8dc0c67599492bd6e90fca4a034e29e334ef88
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 827573
Reviewed-on: https://chromium-review.googlesource.com/1012857
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550721}