Same as for unpack, this allows us to pass through the state reset
code of dEQP without UNIMPLEMENTED errors, while still throwing
asserts if they are set to non-default values.

BUG=angleproject:901,angleproject:512

Change-Id: I0ce0258b0e91eb83c066c241693aaa5c164b2989
Reviewed-on: https://chromium-review.googlesource.com/257131Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>