TabSpecificContentSettings no longer knows about MediaStreamDeviceController
To prepare TSCS for componentising, this CL removes the knowledge about MSDS out of TSCS, by pulling out MSDS-specific processing from TSCS to MSDS.
Some tests had to be changed in a non-trivial way to preserve the coverage, in particular, some TSCS unit-tests needed to become MSDS browsertests (as wiring up everything needed for MSDS would be too messy in a unit test).
BUG=387075,395060
Review URL: https://codereview.chromium.org/
678023002
Cr-Commit-Position: refs/heads/master@{#302068}