(as of May 8)
need links to and tests for general exceptions mark, measure method - why doesn't this return the timing information being stored, it might be of immediate interest? Why are we throwing syntax errors on measure if a calculation in the measure method is negative, or a value is 0? Those are hardly syntactical errors. I am not convinced that throwing at all in those cases is optimal, this would lead to developers always wrapping the measures method inside either conditionals, or more likely try/catch clauses. Particularily the latter is quite slow, and would lead to developers slowing down their code when they actually wanted to speed it up. Would a better way be to always store e.g. "-1" in those cases, and let any analytics scripts (which are presumably less time-critical) deal with the errors instead? I am not sure why we need to handle such cases exceptionally at all, sorry if I have missed that discussion.
The text is hard to understand, and can do with a rewrite. Who is to ensure the information is only available to the server, does this mean javascript cannot send it off to another server for analysis there? What is the root document, the top level document, or the cross-origin iframe where the measurements are made? Standard nomenclature is normally "origin", not "domain" or "server".
"If both the startMark and endMark arguments are not" => "If neither ... nor ... is" Vendor prefixes and monotonic clock - uses slightly different language and markup than other specs.