The currently bound framebuffer affects some dirty bits.  This means
that processing those dirty bits temporarily use data from a framebuffer
that's about to be changed.  At best, that creates unnecessary dirty
bits in the Vulkan pipeline description.

Bug: angleproject:3204
Change-Id: Ie001d6c8fcc61af2e78cf2cb58a1691d8b735ff3
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1639750
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>