Implement URLSearchParams.sort()

Spec:
https://url.spec.whatwg.org/#dom-urlsearchparams-sort

Interoperability and Compatibility risk:
Firefox https://bugzilla.mozilla.org/show_bug.cgi?id=1331864 and
WebKit https://bugs.webkit.org/show_bug.cgi?id=167154 have implemented
it.

web-platform-tests:
url/urlsearchparams-sort.html

Feature dashboard:
https://www.chromestatus.com/feature/5632900720492544

Bug: 682143
Change-Id: I5a1831503579079d3d95de3028b2f8195192c88d
Reviewed-on: https://chromium-review.googlesource.com/515243
Commit-Queue: Takeshi Yoshino <tyoshino@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Cr-Commit-Position: refs/heads/master@{#482590}
20 files changed