Web Inspector: Flame Chart. draw background for the FlameChart overview pane with the CPU aggregated data.
https://bugs.webkit.org/show_bug.cgi?id=112823

Reviewed by Yury Semikhatsky.

The idea of the patch is to collect the data about stack depth for the each X
and draw a line with help of this data.

* inspector/front-end/FlameChart.js:
(WebInspector.FlameChart):
(WebInspector.FlameChart.prototype.onResize):
(WebInspector.FlameChart.prototype._drawOverviewCanvas):
(WebInspector.FlameChart.prototype.update):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@146448 268f45cc-cd09-0410-ab3c-d52691b4dbfc