gl::State::mDirtyCurrentValues is a second tier of
gl::State::DIRTY_BIT_CURRENT_VALUES bit.
Marking mDirtyCurrentValues dirty during context switches
treats them in the same way as other gl::State::mDirtyBits are treated.

This has regressed in
https://chromium-review.googlesource.com/c/angle/angle/+/722423
where individual current values bits were squashed into one.

Bug: chromium:920033
Change-Id: I778515f11c975f8d88bd2d8c08c49160fd011497
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1545009Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>