Translator: Correctly respect precision of gl_FragColor/Data These builtins are declared with a mediump precision. However, during translation to Vulkan GLSL, the precision was not output and as such glslang treated them as highp. Discovered through comparison with SPIR-V output from ANGLE which included more RelaxedPrecision operations. Bug: angleproject:4889 Change-Id: I7974478e87ad20115345d679f8f035492be1f349 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3062204 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>