Rename devtools-timeline trace category to devtools.timeline

Also use Timeline event names instead of instrumented method names as we actually instrument only parts of the methods.

BUG=361045

Review URL: https://codereview.chromium.org/247463002

git-svn-id: svn://svn.chromium.org/blink/trunk@172151 bbb929c8-8fbe-4397-9dbb-9b2b20218538