Chrome Version       : 65.0.3287.0
OS Version: 10194.0.0

What steps will reproduce the problem?
1. Start Chrome fresh
2. Open website that calls something like "const foo = new MediaSource();"
3. Check out trace

What is the expected result?
It should be less than 5ms.

What happens instead of that?
It is almost 60ms. See trace attached.
 

Deleted: trace_nexus-5-first-load-more-categories.json 9.7 MB

trace_nexus-5-first-load-more-categories.json 9.7 MB View Download

Chrome Version       : 65.0.3287.0
OS Version: 10194.0.0

What steps will reproduce the problem?
1. Start Chrome fresh
2. Open website that calls something like:

  const video = document.createElement('video');
  const mediaSource = new MediaSource();
  video.src = URL.createObjectURL(mediaSource);

3. Check out trace

What is the expected result?
The event "MediaSource::attachToElement" should last less than 5ms.

What happens instead of that?
It is almost 60ms. See trace attached.
 

Deleted: trace_nexus-5-first-load-more-categories.json 9.7 MB

trace_nexus-5-first-load-more-categories.json 9.7 MB View Download