[WebTiming] Exporting flattened DOMTiming data

   Discussions with several browser developers suggest exporting a flattened
data structure containing
all the DOMTiming objects on the page. Doing so allows site developers to
send the all the timing information
back for analysis without travelling the entire DOM tree. It helps minimize
the observer effect of the client
side instrumentations.

  The current proposal is to add an additional interface to the
WebTiming<http://dev.w3.org/2006/webapi/WebTiming/>draft that exports
this block of
timing data, including the url, type and probably id associated with each
DOMTiming object. The implementation
details are mostly left to UAs at this time.

  Another question is should this flattened data contain only DOMTiming
objects currently in the DOM or all those
ever exist since the page starts. My preference is the first case but it's
up to debate.

  I imagine this to be a rather significant change in terms of UA
implementations so I would like to bring
this up for discussion.

cheers,
Zhiheng