Add tracing and timing info to GN

This allows outputting a performance summary of time blame, as well as writing a chrome trace log.

Moves the help printing functions from command_help to standard_out since I re-used the coloring routines for timing output.

BUG=
R=scottmg@chromium.org

Review URL: https://codereview.chromium.org/24331007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@224749 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 224749