Vulkan: Mark some Resource APIs are protected. This clarifies what is supposed to be called from outside the class to what should be called internally. The read/write dependency management is accessible publically. The command buffer access however is private and should be only used within the class. Bug: angleproject:2539 Change-Id: Ic25b589d4009de62633d13546be596ecafd0b175 Reviewed-on: https://chromium-review.googlesource.com/1066555 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Luc Ferron <lucferron@chromium.org> Reviewed-by: Frank Henigman <fjhenigman@chromium.org>