Add HeapListHashSet.

R=ager@chromium.org, haraken@chromium.org, mikhail.pozdnyakov@intel.com, zerny@chromium.org
BUG=

Review URL: https://codereview.chromium.org/256143002

git-svn-id: svn://svn.chromium.org/blink/trunk@173297 bbb929c8-8fbe-4397-9dbb-9b2b20218538
TimelinePanel: replace a few properties in TimelineModel.Record with initiator property.

BUG=321045

Review URL: https://codereview.chromium.org/257363003

git-svn-id: svn://svn.chromium.org/blink/trunk@173298 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Removed unused adjustOverflow parameter.

Review URL: https://codereview.chromium.org/266993002

git-svn-id: svn://svn.chromium.org/blink/trunk@173299 bbb929c8-8fbe-4397-9dbb-9b2b20218538