Web Inspector: [Network] Timeline bars and dividers are positioned in different coordinate systems.
https://bugs.webkit.org/show_bug.cgi?id=109943

Reviewed by Pavel Feldman.

Look at network log: red bar (on load) is positioned to the right of
the last required load.

This is incorrect. For exmaple, in case of short event it should be
positioned in the center of the bar.

* inspector/front-end/DataGrid.js:
Fix - hidden columns can have non-zero width.
* inspector/front-end/NetworkPanel.js: Use correct width for calculator.
* inspector/front-end/networkLogView.css: Removed parasite paddinds.
Extracted common absolute "paddings".


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@143902 268f45cc-cd09-0410-ab3c-d52691b4dbfc