v3 UI should use four sig-figs to label y-axis of the main charts

v3 UI should use four sig-figs to label y-axis of the main charts
https://bugs.webkit.org/show_bug.cgi?id=152779

Reviewed by Antti Koivisto.

Increase the number of significant figures used in the main charts to four as done in v2 UI.

* public/v3/pages/chart-pane.js:
(ChartPane.constructor): Create a formatter with four significant figures.
* public/v3/pages/page-with-charts.js:
(PageWithCharts.mainChartOptions): Increase the width of y-axis labels.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@194652 268f45cc-cd09-0410-ab3c-d52691b4dbfc