Vulkan: Skip pool eviction when cache is disabled When cache is disabled, every time a new descriptorSet is allocated and bind to program, the previous descriptorSet will be added to the tail of garbage list, and the new descriptorSet is retrieved from the head of the garbage list, if its GPU usage has been completed. This means there will never have a situation that significant amount of descriptorSets are needed, therefore no need for pool eviction. One possible situation is that at one point you need a lot of descriptorSets and then after a while you only need small amount of descriptorSets. In that case we could delete the excessive unused descriptorSets. But since they are all allocated from a pool, as long as there is still one descriptorSet in the pool is used, you still can't destroy the pool. This means eviction is really not much useful when cache is disabled. Bug: angleproject:372268711 Change-Id: Id77b181b64e122f576ee43d11c39dc75bd681dcf Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5941126 Reviewed-by: Yuxin Hu <yuxinhu@google.com> Commit-Queue: Charlie Lao <cclao@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>