Most of autoplay/feature-policy tests are passing after  issue 794631  got fixed (and I am cleaning up test expectations in https://crrev.com/c/1169916).  But, there is one remaining failure that needs to be taken care of: media/autoplay/document-user-activation-feature-policy-iframe-no-gesture.html 

Interestingly, this test passes when run separately.  So far I have only been able to repro a failure when running this test together with other feature policy / autoplay tests:

    $ cat $HOME/scratch/list
    http/tests/media/autoplay/document-user-activation-cross-origin-feature-policy-delegation.html
    http/tests/media/autoplay/document-user-activation-cross-origin-feature-policy-disabled.html
    http/tests/media/autoplay/document-user-activation-cross-origin-feature-policy-gesture.html
    http/tests/media/autoplay/document-user-activation-cross-origin-feature-policy-header.html
    http/tests/media/autoplay/document-user-activation-feature-policy-alternating.html
    http/tests/media/autoplay/document-user-activation-feature-policy-iframe-no-gesture.html
    http/tests/media/autoplay/document-user-activation-feature-policy-same-origin.html
    http/tests/media/autoplay/document-user-activation-iframe-delegation.html
    virtual/user-activation-v2/http/tests/media/autoplay/document-user-activation-cross-origin-feature-policy-delegation.html
    virtual/user-activation-v2/http/tests/media/autoplay/document-user-activation-cross-origin-feature-policy-disabled.html
    virtual/user-activation-v2/http/tests/media/autoplay/document-user-activation-cross-origin-feature-policy-gesture.html
    virtual/user-activation-v2/http/tests/media/autoplay/document-user-activation-iframe-delegation.html

    $ DISPLAY=:20 third_party/WebKit/Tools/Scripts/run-webkit-tests -t rel --no-retry --additional-driver-flag=--site-per-process http/tests/media/autoplay/document-user-activation-feature-policy-iframe-no-gesture.html --iterations=20 --test-list=$HOME/scratch/list

The failure looks as follows:

    CONSOLE WARNING: line 68: The AudioContext was not allowed to start. It must be resumed (or created) after a user gesture on the page. https://goo.gl/7K7WLu
    CONSOLE WARNING: line 68: The AudioContext was not allowed to start. It must be resumed (or created) after a user gesture on the page. https://goo.gl/7K7WLu
    This is a testharness.js-based test.
    FAIL Test that autoplay is still disabled if there is no gesture, but autoplay is switched on. assert_equals: expected true but got false
    Harness: the test ran to completion.