shiny/driver/windriver: move buffer swizzling off message pump thread

Message pump thread handles all window messages and need to be
as responsive as possible. Do buffer swizzling on a different
from message pump thread.

Change-Id: If5ddbc32934d1e5627373d725a24fa7ee8070fee
Reviewed-on: https://go-review.googlesource.com/22183
Reviewed-by: David Crawshaw <crawshaw@golang.org>
1 file changed