The W3C WebPerf working group has been incubating a number of specifications, which we’d like to propose to transition to WICG for wider review, feedback, etc. Specifically…
This specification defines an interface for web applications to access runtime performance information of the browser event loop, enabling them to identify and fix issues that cause delayed rendering, processing of input, and other critical work necessary to deliver a smooth and responsive user experience.
This document defines a generic reporting framework which allows web developers to associate a set of named reporting endpoints with an origin. Various platform features (like Content Security Policy, Network Error Reporting, and others) will use these endpoints to deliver feature-specific reports in a consistent manner.
Network Error Logging
This document defines a mechanism that enables developers to declare a network error reporting policy for a web application. A user agent can use this policy to report encountered network errors that prevented it from successfully fetching requested resources.
None of the above have been implemented in any browser. That said, some (e.g. Reporting, NEL) may see that change very soon (with my optimist hat on :-)).