Revert 171450 "API functions returning Promises should not throw..."

> API functions returning Promises should not throw exceptions.
>
> http://heycam.github.io/webidl/#es-operations states that an API returning
> a Promise should return a rejected Promise when an error occurs rather than
> throwing an exception.
>
> BUG=359386, 362992
> R=nbarth@chromium.org, eroman@chromium.org
>
> Review URL: https://codereview.chromium.org/232563003

TBR=yhirano@chromium.org

Review URL: https://codereview.chromium.org/240803003

git-svn-id: svn://svn.chromium.org/blink/trunk@171848 bbb929c8-8fbe-4397-9dbb-9b2b20218538