WebGL 2 seems to be ES300 context and will fail the
ValidateGetBooleani_v at context->getClientVersion() >= ES_3_1.

Also for getIndexedParameter pname==GL_COLOR_WRITEMASK, the length
shall be 4.

Bug: angleproject:4394, chromium:1058744
Change-Id: Ia60506b6b1f120ed06acbcea0cb1f4581c70b32b
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2191424Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Shrek Shao <shrekshao@google.com>