WEBGL_draw_elements_no_range_check - dropped as an extension. This functionality would be better to implement just as a part of WebGL 2 at this point, if it is decided that the tradeoffs offered here are good.
WEBGL_security_sensitive_resources - This is a very ambitious extension. While the functionality is desirable, it's hard to implement and could hurt performance in a major way in some cases. For example delta color compression in NVIDIA GPUs would likely have to be disabled due to the timing requirements. So I don't honestly see this being worth the effort, though maybe others disagree.