Expose the EGL Display Context Set in the DisplayState. This will let the Vulkan back-end iterate through and flush pending command buffers in other Contexts. Bug: angleproject:5664 Change-Id: I0d22eb68fa754a97b4836ec8c59ff8c6e5ef2d96 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3668145 Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>