Web Inspector: Flame Chart. Support scroll and zoom with help of mouse wheel.
https://bugs.webkit.org/show_bug.cgi?id=112337

Reviewed by Yury Semikhatsky.

New member variable _xOffset were introduced.

* inspector/front-end/FlameChart.js:
(WebInspector.FlameChart):
(WebInspector.FlameChart.prototype._onMouseMove):
(WebInspector.FlameChart.prototype._adjustXOffset):
(WebInspector.FlameChart.prototype._adjustXScale):
(WebInspector.FlameChart.prototype._onMouseWheel):
(WebInspector.FlameChart.prototype._coordinatesToNodeIndex):
(WebInspector.FlameChart.prototype.onResize):
(WebInspector.FlameChart.prototype.draw):
(WebInspector.FlameChart.prototype._scheduleUpdate):
(WebInspector.FlameChart.prototype.update):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@145807 268f45cc-cd09-0410-ab3c-d52691b4dbfc