Add KHR_blend_equation_advanced_coherent * Added this extension to registry_xml.py. Bug: angleproject:42262258 Change-Id: I2d69982b9ec876e3c21346039ed78aa21b1a1896 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5634379 Commit-Queue: Amirali Abdolrashidi <abdolrashidi@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Cody Northrop <cnorthrop@google.com>