In this case the draw surface should be unbound, but ANGLE had been
skipping this case (and handling it internally). This caused a crash on
Linux Intel. Now makeCurrent is actually called on the driver with
drawSurface mDummyPbuffer.
Bug: chromium:988440
Change-Id: Ifae7a828455eb67e516a47515ec6c24cc36e3c2b
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1808719
Commit-Queue: Jonah Ryan-Davis <jonahr@google.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
