Implements Windows system tracing.

This CL brings the tracing information into the resulting JSon.

As tracing needs administrator rights, we assume that Chrome is launched
as administrator.

To be able to view events, the traceviewer part must land first.
see: https://codereview.appspot.com/51300043/

BUG=

Review URL: https://codereview.chromium.org/171143002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255818 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255818