Add inttest for +[CWVWebView userAgentProduct]

Bug: 862537
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: Ie69f12655aae22a9c48452d86ef27bafafadae68
Reviewed-on: https://chromium-review.googlesource.com/1132912
Commit-Queue: Hiroshi Ichikawa <ichikawa@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575534}
7 files changed