[Telemetry] add CC to the trace profiler

It gives an enhanced view to the recorded traces. Specifically
it gives a visual notion of where the SpeedIndex would be measured.

BUG=

Review URL: https://codereview.chromium.org/136573006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246376 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246376