Interactive chart component provides two duplicate API for highlighting points

Interactive chart component provides two duplicate API for highlighting points
https://bugs.webkit.org/show_bug.cgi?id=141234

Reviewed by Chris Dumez.

Prior to this patch, the interactive chart component supported highlightedItems for finding commits
on the main charts page and markedPoints to show the two end points in the analysis task page.

This patch merges markedPoints into highlightedItems.

* public/v2/app.js:
(App.AnalysisTaskController._fetchedRuns): Use highlightedItems.
* public/v2/chart-pane.css:
* public/v2/index.html: Ditto.
* public/v2/interactive-chart.js:
(App.InteractiveChartComponent._constructGraphIfPossible): Make this._highlights an array instead of
array of arrays. Also call _highlightedItemsChanged at the end to fix the bug that we never highlight
items if highlightedItems was set before the initial layout.
(App.InteractiveChartComponent._relayoutDataAndAxes):
(App.InteractiveChartComponent._updateHighlightPositions): Now that highlights are circles instead of
vertical lines, just set cx and cy as done for other "dots".
(App.InteractiveChartComponent._highlightedItemsChanged): Exit early only if _clippedContainer wasn't
already set; i.e. _constructGraphIfPossible hasn't been called. Also updated the logic to accommodate
the fact this._highlights is an array of elements instead of an array of arrays of elements. Finally,
set the radius of highlight circles here.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@179611 268f45cc-cd09-0410-ab3c-d52691b4dbfc