Revert "Implement gl_FragDepth for GLES SL 3.0" assertion failures in WebGL2 CTS. This reverts commit 544809610a131fe7040f2212789c62e212bbaf24. Change-Id: I2e0c7045c5b6ef9031a6e6c5916504fe68f51077 Reviewed-on: https://chromium-review.googlesource.com/287910 Reviewed-by: Geoff Lang <geofflang@chromium.org> Tested-by: Geoff Lang <geofflang@chromium.org>