REGRESSION: v2 UI reports a higher memory usage

REGRESSION: v2 UI reports a higher memory usage
https://bugs.webkit.org/show_bug.cgi?id=145151

Reviewed by Chris Dumez.

The bug was caused by v2 UI using 1000 to divide the number of bytes instead of by 1024 as done in v1.
Fixed the bug by manually implementing the formatter as done in v1.

* public/v2/manifest.js:
(App.Manfiest._formatBytes): Added.
(App.Manifest._formatFetchedData): Use _formatByte instead of format('s').

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@184531 268f45cc-cd09-0410-ab3c-d52691b4dbfc