DevTools: process events from all threads in TimelineTraceEventBindings

We used to process only main thread events in both TraceEventBindings
and TimelineFrameModel. This drops the filtering by thread from TracingModel
and lets its clients process all events from the inspected target, performing
filtering on their own.
Also, this forks the enum for thread event names from that of timeline model --
they may occasionally overlap, but essentially these are two different enums.

BUG=361045

Review URL: https://codereview.chromium.org/301593002

git-svn-id: svn://svn.chromium.org/blink/trunk@174955 bbb929c8-8fbe-4397-9dbb-9b2b20218538