New perf dashboard doesn't preserve the number of days when clicking on a dashboard...

New perf dashboard doesn't preserve the number of days when clicking on a dashboard chart
https://bugs.webkit.org/show_bug.cgi?id=141280

Reviewed by Chris Dumez.

Fixed the bug by passing in "since" as a query parameter to the charts page.

Also fixed the styling issue that manifests when a JSON fetching fails on "Dashboard" page.

* public/v2/app.css: Fixed CSS rules for error messages shown in the place of charts.
* public/v2/app.js:
(App.IndexController): Changed the default number of days from one month to one week.
(App.IndexController._sharedDomainChanged): Set "since" property on the controller.
* public/v2/index.html: Pass in "since" property on the controller as a query parameter.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@179661 268f45cc-cd09-0410-ab3c-d52691b4dbfc