This succesfully renders HelloTriangle and some samples but fails on a
lot of tests. In particular it doesn't handle resizing the window and
doesn't have depth or stencil buffers.

BUG=angleproject:891

Change-Id: I16356471b470f764acb38e8dd3589e9c0129829d
Reviewed-on: https://chromium-review.googlesource.com/290770Tested-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>