DevTools: Server Timing values should be in milliseconds

This is a breaking change. This feature landed in August, but just announced
this week (twitter.com/paul_irish/status/829090506084749312).
Users discovered the original patch used seconds values, but the Server
Timing spec dictates these as DOMHighResTimeStamp which are milliseconds.

BUG=594800

Review-Url: https://codereview.chromium.org/2689833002
Cr-Commit-Position: refs/heads/master@{#450244}
2 files changed