This can now use the VertexArrayVk dirty bits. It also
seems as though there are a couple caching bugs with the
LineLoopHandler.

Bug: angleproject:2389
Change-Id: I8af73f4acf56768ed9c68395349ba96acfbe9666
Reviewed-on: https://chromium-review.googlesource.com/989259
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Frank Henigman <fjhenigman@chromium.org>
Reviewed-by: Luc Ferron <lucferron@google.com>