Some methods in GraphicsContextGL and WebGL2RenderingContext exist only for the non-ANGLE code path. Since WebGL 2.0 is infeasible to implement without ANGLE, and has already been disabled for the non-ANGLE code path (!USE(ANGLE)), these methods and overrides should be removed.
As one example, WebGLRenderingContextBase::validateIndexArrayConservative should be removed from the non-ANGLE code path, and the override removed from WebGL2RenderingContext.
After more thought, fixing up the remaining WebGL 2.0 conformance issues is higher priority than this cleanup. Downgrading to P3 and unassigning myself for the moment.