Vulkan: Only calculate variable locations once Variable locations and descriptor set/binding values are calculated multiple times: - Compiling GLSL->SPIR-V - Creating the Vulkan pipeline layout - Updating descriptor sets These values should instead be calculated once and reused throughout since they won't change without recompiling the shader program. Bug: angleproject:3570 Change-Id: I5d8767b3b2e2f741aade7fec9991eea53ee2eb98 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2067101 Commit-Queue: Tim Van Patten <timvp@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>