Remove the dependency on OpenGL32.lib by loading all WGL functions. BUG=angle:879 Change-Id: I1a10a86b710cb0c76be1907136345bcac078da4d Reviewed-on: https://chromium-review.googlesource.com/249740 Reviewed-by: Geoff Lang <geofflang@chromium.org> Tested-by: Geoff Lang <geofflang@chromium.org>