UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.62 Safari/537.36

Example URL:

Steps to reproduce the problem:
1. send the request 
2. run some busy tasks during some times
3. when the network fetch finished, the `content download time` show very long time

What is the expected behavior?
It should be the network download time only.

What went wrong?
I feel it contains the JS got the data after the tasks finished. 

It should be the network download time only.

And if want to show the data is available for JS , I think should be another panel for it.

Did this work before? N/A 

Chrome version: 62.0.3202.62  Channel: stable
OS Version: OS X 10.13.0
Flash Version: 

here is the test code
```
var addRandomConsole = (n = 0) => {
  if (--n > 0) {
    console.log('random console :%s', n)
    addRandomConsole(n)
  }
}
  fetch('//www.google.com?t='+ Date.now()).then(console.log).catch(console.error)
  console.time('dump')
  addRandomConsole(1000)
  console.timeEnd('dump)
```