Always update HALF_FLOAT_OES type to HALF_FLOAT on Desktop GL. TEST=webgl_conformance_gl_passthrough_tests on Linux/Windows BUG=angleproject:2231 Change-Id: I17c7d693e2b75726e2478925e0f22963de6ab819 Reviewed-on: https://chromium-review.googlesource.com/763987 Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org>