DevTools: adopt existing Timeline tests for tracing based Timeline

All existing timeline tests under inspector/timeline and http/tests/inspector are copied into inspector/tracing and http/tests/tracing correspondingly. All tests under .../inspector/timeline/tracing are moved to .../inspector/tracing too.

In that folder the tests are run with "Timeline based on trace events" experiment on (see changes in InspectorView.js), while the old tests continue to use old Timeline implementation. We are going to keep both implementations and tests for them until we are sure that the new implementation is stable enough and can be moved out of experimental. At that point old implementation will be removed along with the old tests.

BUG=398785

Review URL: https://codereview.chromium.org/477153005

git-svn-id: svn://svn.chromium.org/blink/trunk@180815 bbb929c8-8fbe-4397-9dbb-9b2b20218538