Vulkan: Avoid flushCommandsAndEndRenderPass for readonlyDS switch When we switch to read only depth stencil mode, right now we always call flushCommandsAndEndRenderPass, even though the started render pass is empty and loadOp is load. This flush will cause render pass actually submitted and color attachment being cleared and then color attachment gets loaded in the subsequent render pass. In this CL, we only flush if the depthStencil attachment has clear or written This CL save one renderPass for the following app traces: antutu_refinery, aztec_ruins, manhattan_10, manhattan_31. Bug: b/290833623 Change-Id: I13b7a968d797b4c913f1cfbe9677d9b8abe791d2 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4674087 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Yuxin Hu <yuxinhu@google.com> Commit-Queue: Charlie Lao <cclao@google.com>