Store unsaved trace data on exit.

This CL enables chromeos chrome startup trace when chrome in restarted on
user log in: startup trace should be saved to disk on process exit if
"trace-startup-duration" period has not ended yet.

BUG=346913
TEST=manual

Review URL: https://codereview.chromium.org/359473006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@281061 0039d316-1c4b-4281-b951-d872f2087c98
5 files changed