Implements:
* Event loop event waiting (no busy loop)
** Skia timers
* Proper window sizing and resizing
* MSAA on X11 (previously it did not use MSAA at all)
* Changes requested colorspace from 565 to 8888
to match non-SDL variants
* Context creation clearing (color and stencil mask)
* Opens the window in 640x480 by default on desktop.
Removes dead code.
BUG=skia:4733
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1578173002
Review URL: https://codereview.chromium.org/1578173002
abc0c8216b