Disable rendering.mobile/yahoo_answers_mobile_2018  on webview platforms

Bug:873013
NOTRY=true

TBR=sadrul@chromium.org, vmiura@chromium.org

Change-Id: I191cc697f66945c327c2c8a4bdf5ecb1029e041b
Reviewed-on: https://chromium-review.googlesource.com/1170359
Reviewed-by: Ned Nguyen <nednguyen@google.com>
Commit-Queue: Ned Nguyen <nednguyen@google.com>
Cr-Commit-Position: refs/heads/master@{#582008}