Fix misc bugs and typos in app.js

Fix misc bugs and typos in app.js
https://bugs.webkit.org/show_bug.cgi?id=138946

Reviewed by Benjamin Poulain.

* public/v2/app.js:
(App.DashboardPaneProxyForPicker._platformOrMetricIdChanged):
(App.ChartsController.init):
(App.buildPopup): Renamed from App.BuildPopup.
(App.InteractiveChartComponent._constructGraphIfPossible): Fixed the bug that we were calling
remove() on the wrong object (an array as opposed to elements in the array).
(App.InteractiveChartComponent._highlightedItemsChanged): Check the length of _highlights as
_highlights is always an array and evalutes to true.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@176435 268f45cc-cd09-0410-ab3c-d52691b4dbfc