DevTools: add initial support for console.time/timeEnd in tracing based Timeline

Existing async events with category blink.timeline are reused for DevTools needs. The events will be shown as marker events, i.e. as markers on the Timeline overview.

BUG=361045
R=caseq@chromium.org

Review URL: https://codereview.chromium.org/497493002

git-svn-id: svn://svn.chromium.org/blink/trunk@180711 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Auto-rebaseline for r180708

http://src.chromium.org/viewvc/blink?view=revision&revision=180708

BUG=401592
TBR=robhogan@gmail.com

Review URL: https://codereview.chromium.org/489383003

git-svn-id: svn://svn.chromium.org/blink/trunk@180712 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: only events with phase "I" should be recognized as instant events

After r178641 we don't use "i" for instant events in Blink. Support for "i" is removed.

BUG=None
R=alph@chromium.org

Review URL: https://codereview.chromium.org/493083002

git-svn-id: svn://svn.chromium.org/blink/trunk@180713 bbb929c8-8fbe-4397-9dbb-9b2b20218538