This CL makes it possible to build sky_shell on Linux. It doesn't do much, but
it doesn't crash on startup. The goal is to evetually be able to test sky_shell
on the bots and to be able to run the test_sky on Mac.
R=eseidel@chromium.org
Review URL: https://codereview.chromium.org/1202323002.
Previously, we weren't scheduling a visual update when our surface was created,
so we'd just continue to show black until the author requested a new animation
frame. After this CL, we schedule a visual update as soon as our surface is
created.
As part of this change, I've removed knowledge of the GPU delegate from
PlatformView. Now, all the calls from PlatformView to the GPU system bounce
through the UI delegate, which serializes the commands with other commands from
the UI engine to the GPU rasterizer.
R=eseidel@chromium.org
Review URL: https://codereview.chromium.org/974483004
