ContextImpl: only expose getResetStatus for robustness This will allow each backend to implement this method separately. The current set of ContextImpl methods used for robustness are slightly D3D-centric. BUG=angleproject:1463 Change-Id: I101f8ada2c49de4cf110db48b1e8380c52b50fb2 Reviewed-on: https://chromium-review.googlesource.com/365829 Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Corentin Wallez <cwallez@chromium.org>