The rows in the analysis results table should be expandable

The rows in the analysis results table should be expandable
https://bugs.webkit.org/show_bug.cgi?id=154427

Reviewed by Chris Dumez.

Added "(Expand)" link between rows that have hidden points. Upon click it inserts the hidden rows.

We insert around five rows at a time when there are hundreds of hidden points but we also avoid leaving
behind expandable rows of less than two rows.

Also fixed a bug in CustomizableTestGroupForm that getElementsById would throw in the shipping Safari
because getElementsById doesn't exist on Element.prototype by using class name instead.

* public/v3/components/analysis-results-viewer.js:
(AnalysisResultsViewer):
(AnalysisResultsViewer.prototype.setCurrentTestGroup): Removed superfluous call to render().
(AnalysisResultsViewer.prototype.setPoints): Always show the start and the end points.
(AnalysisResultsViewer.prototype.buildRowGroups):
(AnalysisResultsViewer.prototype._buildRowsForPointsAndTestGroups): Add an instance of ExpandableRow which
shows a "(Expand)" link to show hidden rows here.
(AnalysisResultsViewer.prototype._expandBetween): Added. Expands rows between two points.
(AnalysisResultsViewer.cssTemplate): Added rules for "(Expand)" links.
(AnalysisResultsViewer.ExpandableRow): Added.
(AnalysisResultsViewer.ExpandableRow.prototype.resultContent): Added. Overrides what's in the results column.
(AnalysisResultsViewer.ExpandableRow.prototype.heading): Added. Generates "(Expand)" link.

* public/v3/components/customizable-test-group-form.js:
(CustomizableTestGroupForm.prototype._computeRootSetMap): Use getElementsByClassName instead of
getElementById.
(CustomizableTestGroupForm.prototype._classForLabelAndRepository): Renamed from _idForLabelAndRepository.
(CustomizableTestGroupForm._constructRevisionRadioButtons): Set class name instead of id.

* public/v3/components/results-table.js:
(ResultsTable.prototype.render): Don't generate radio buttons to select a row when root set is missing;
e.g. for rows that show "(Expand)" links.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@196792 268f45cc-cd09-0410-ab3c-d52691b4dbfc