WebGLRenderingContexts should initialize all context state in initializeNewContext()
<rdar://problem/113261547>
Pull request: https://github.com/WebKit/WebKit/pull/16312
Committed 266579@main (2aadd417b2ce): <https://commits.webkit.org/266579@main> Reviewed commits have been landed. Closing PR #16312 and removing active labels.