This class has its fingers in a lot of other classes. In particular,
we will likely need to revisit the context lost handling methods when
we implement the robustness extensions on top of desktop GL. For now,
we can leave them tied pretty tightly to the D3D implementation.

BUG=angle:795

Change-Id: I9b3ac90dfd393f52c5b49bc2bd6b97fb5536ed91
Reviewed-on: https://chromium-review.googlesource.com/228916Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>