Currently some web tests load resources with file:// urls. These file URLs are also remapped in content_shell to resolve full file path, see https://codesearch.chromium.org/chromium/src/content/shell/renderer/web_test/blink_test_helpers.cc?q=blink_test_helpers&sq=package:chromium&g=0&l=175 . This approach doesn't work on systems that load these tests from https origin, specifically Android and Fuchsia. This issue exists in the following smoke tests:

device_orientation/motion/add-listener-from-callback.html
fast/speech/scripted/speechrecognition-re-restart.html
presentation/presentationconnectionavailableevent-ctor-mock.html
webmidi/permission.html

This can be solved by using relative urls that don't include protocol, e.g. 
<script src="/gen/layout_test_data/mojo/public/js/mojo_bindings.js">