TOutputGLSLBase::visitLoop clarify the function slightly Since only for loops can be unrolled, handle each type of loop only once. This improvement was going to be part of a do-while workaround for Mac that will instead be done at the AST level. BUG=angleproject:891 Change-Id: Ic8ecf41aa6d9abd7a01c2230e908c85152f52b62 Reviewed-on: https://chromium-review.googlesource.com/302332 Tryjob-Request: Corentin Wallez <cwallez@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Tested-by: Corentin Wallez <cwallez@chromium.org>