Vulkan: Add entry points for GL_QCOM_shading_rate Bug: angleproject:7172 Change-Id: I837d2697d95c44f47a2fab7411cfd87a4ec65e90 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3599873 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: mohan maiya <m.maiya@samsung.com>