Add initial SHM-only Wayland Ozone implementation

This is just the bare minimum to get a window on the screen.

Things like cursor handling, input handling, and vsync provider will come in
subsequent commits.

BUG=578890

Review URL: https://codereview.chromium.org/1610683003

Cr-Commit-Position: refs/heads/master@{#372770}
18 files changed