Pass Context to Fence Impl methods. This is needed for the error refactoring and also for the Vulkan implementation. Bug: angleproject:2738 Change-Id: I4e1bed7f67ef17feb5554b5838a2ed5feb22bba0 Reviewed-on: https://chromium-review.googlesource.com/1150091 Reviewed-by: Yuly Novikov <ynovikov@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>