This is based on the Skia Implementation.
More on the project can be found here:
https://docs.google.com/a/chromium.org/document/d/1_4LAnInOB8tM_DLjptWiszRwa4qwiSsDzMkO4tU-Qes/edit#heading=h.p97rw6yt8o2j
The V8 Tracing platform will replace the isolate->event_logger().
But since the current embedders (namely chromium) currently use the isolate->event_logger, I made the default implementation (event-tracer) call into isolate->event_logger if an event_logger was set.
Once the embedders properly implement the interface (for example in chromium it would look like this: https://codereview.chromium.org/707273005/), the default implementation will be doing nothing.
Once the embedders side is fixed, we will change how V8 uses the tracing framework beyond the call from Logger:CallEventLogger. (which would also include a d8 implementation)
BUG=v8:4560
LOG=N
Review URL: https://codereview.chromium.org/988893003
Cr-Commit-Position: refs/heads/master@{#32959}
