Fix tooltip title in radar charts (#6238)

Author: kurkle

src/controllers/controller.radar.js

@@ -27,13 +27,6 @@ module.exports = DatasetController.extend({
 		return this.chart.scale.id;
 	},
 
-	/**
-	 * @private
-	 */
-	_getIndexScaleId: function() {
-		return this.chart.scale.id;
-	},
-
 	datasetElementType: elements.Line,
 
 	dataElementType: elements.Point,

test/specs/controller.radar.tests.js

@@ -444,7 +444,7 @@ describe('Chart.controllers.radar', function() {
 		expect(meta1.data[0]._model.radius).toBe(20);
 	});
 
-	it('should return same id for index and value scale', function() {
+	it('should return id for value scale', function() {
 		var chart = window.acquireChart({
 			type: 'radar',
 			data: {
@@ -460,7 +460,6 @@ describe('Chart.controllers.radar', function() {
 		});
 
 		var controller = chart.getDatasetMeta(0).controller;
-		expect(controller._getIndexScaleId()).toBe('test');
 		expect(controller._getValueScaleId()).toBe('test');
 	});
 });