Tidy up ConsoleMessage callstack inclusion, fix Worker console crashes

Follow up r181319 (+ r180544) and annotate ConsoleMessages from
console.count() and console.timeEnd() with a call stack.

Not doing so broke the WorkerConsole::reportMessageToConsole()
assumption that a ConsoleMessage has a call stack. An unnecessary
assumption to make, so instead have it mirror how "non-Worker" console
messages are handled when reported, and allow "stackless" messages.

R=kozyatinskiy,aandrey,jochen
BUG=413223

Review URL: https://codereview.chromium.org/562683003

git-svn-id: svn://svn.chromium.org/blink/trunk@182056 bbb929c8-8fbe-4397-9dbb-9b2b20218538