GitLab

Details:
- Implement CWVBackForwardList: a equivalent of https://developer.apple.com/documentation/webkit/wkbackforwardlist
- Implement CWVBackForwardListItem: a equivalent of https://developer.apple.com/documentation/webkit/wkbackforwardlistitem
- Implement |backForwardList| property in CWVWebView and -[CWVWebView goToBackForwardListItem:]

Bug: 1021830
Change-Id: Ia04f5197fb1eb03b1f59955068f00af1022fc2a9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1928460
Commit-Queue: Jiajun Ou <garzonou@google.com>
Reviewed-by: Hiroshi Ichikawa <ichikawa@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#723651}