Mac Overlays: Send vsync parameters directly

Mac Overlays: Send vsync parameters directly

The previous attempt was to send the display ID, but, there are two
things to contend with.

1. VSync parameters change wildly -- sometimes a half-interval just
   disappears ... so you need to update your VSync parameters often, or
   they'll be wrong.

2. Computing the VSync parameters is expensive because it creates a
   display link thread, and so on.

This idea of creating a display link for the browser and the gpu,
and hoping that they'd stay in sync, wasn't a good idea. Just send the
parameters directly. We'll need to add some smarts to DisplayLinkMac to
ensure that they're updated frequently.

BUG=515696

Review URL: https://codereview.chromium.org/1297473003

Cr-Commit-Position: refs/heads/master@{#343567}