Allow audio requests in DisplayMediaAccessHandler

This CL adds cases to allow for MEDIA_DISPLAY_AUDIO_CAPTURE requests, which are
expected to originate from getDisplayMedia({audio:true}) calls. In picker UI,
we reuse the existing extensions based picker implementation and offer audio
share option as a radio button. See design doc in the below bug for more
details.

Bug: 896333
Change-Id: Ibde7c011db6806cad52c126f8855b2c3dff5ee74
Reviewed-on: https://chromium-review.googlesource.com/c/1440905
Commit-Queue: Emircan Uysaler <emircan@chromium.org>
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#627334}
3 files changed