New Web Perf API Support in IE11 Preview

As you may have heard, IE11 Preview was released today on the Windows 8.1 Preview. This build of IE supports a few of the new Web Perf APIs we have been working on:

Navigation Timing L2
IE11 now supports Navigation Timing L2. The PerformanceNavigationTiming object contains all the timing attributes supported in performance.timing and performance.navigation in high resolution time, and the required PerformanceEntry attributes: name, entryType, duration, and startTime. As this is just an object that is returned from a supported method call, we haven't prefixed here. As new attributes are stabilized in this emerging standard, we'll consider adding support to those as well.

Lazyload
IE11 has an early implementation for the emerging Resource Priorities specification at the connection management layer. Developers can specify the 'lazyload' attribute to indicate whether a resource is of lower priority. If there is a connection contention, IE will give available TCP connections, or will give a more optimized TCP connection if there is a choice between available connections, to resources that don't have the "lazyload" attribute. IE11 hasn't yet implemented the not blocking window.onload event for 'lazyload' resource or the application level priority changes (don't fetch the load resource until all other non-lazyload resources have started their fetch) yet, as we're still actively discussing those areas in this emerging standard. As this is an attribute on an element, we haven't prefixed attribute.

Thanks,
Jatinder Mann