Vulkan: Make waitForPendingPresent drain work in the calling thread Since we are waiting, there is no point to have work done in CommandProcessor's worker thread. It can just wait and drain the task in the calling thread. This is consistent with waitForResourceUseToBeSubmitted. This allows us to remove mutex and condition variable from SwapchainStatus. Bug: b/269524271 Change-Id: I9d7e17c77c879b6957fc3b74aab02f7f5c9db052 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4257252 Commit-Queue: Charlie Lao <cclao@google.com> Reviewed-by: Ian Elliott <ianelliott@google.com>