Fix GetBooleani_v validation and params length for WebGL OES_draw_buffers_indexed 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/+/2191424 Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Shrek Shao <shrekshao@google.com>