The crash occured due to a lack of marking a context dirty on
eglMakeCurrent(), resulting in a situation where a thread B would
call eglMakeCurrent() but before issuing additional GL calls,
thread A would issue a draw command. Prior to this change, context
state would only be marked dirty on gl calls.

Test: dEQP-EGL.functional.sharing.gles2.multithread.*
dEQP-EGL.functional.multithread.*
dEQP-EGL.functional.render.multi_thread.*
dEQP-EGL.functional.color_clears.multi_thread.*

Bug: b/177602915
Change-Id: I765e0423002a373f94ea459b81b6e6f6942870d2
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2646609Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Doug Horn <doughorn@google.com>