Don't enable/disable sRGB on GLES. glEnable/glDisable GL_FRAMEBUFFER_SRGB isn't meaningful on GLES. BUG=angleproject:1300 Change-Id: I0afd697ed9770e2eb1cdcc851884b90de1a4583c Reviewed-on: https://chromium-review.googlesource.com/334490 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Frank Henigman <fjhenigman@chromium.org>