Always update HALF_FLOAT_OES type to HALF_FLOAT on Desktop GL.
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 <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>
Commit-Queue: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>

ppy/angle,ppy/angle,ppy/angle,ppy/angle