Enable material design media playback UI on all platforms.

This CL switches the default chrome media player UI to be the
material design UI.  It is enabled as the default in the finch
experiment "NewMediaPlaybackUi", so that it can be disabled via
finch if needed.

This CL also makes some small test changes to make them compatible
with the new UI, and rebaselines quite a few layout tests.

BUG=487344
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/1811003002
Cr-Commit-Position: refs/heads/master@{#393557}
8 files changed