Fix bumpy line on smooth data set (#4944)

Linear scale getPixelForValue() method doesn't round the returned value anymore.

src/scales/scale.linear.js

@@ -170,11 +170,10 @@ module.exports = function(Chart) {
 
 			if (me.isHorizontal()) {
 				pixel = me.left + (me.width / range * (rightValue - start));
-				return Math.round(pixel);
+			} else {
+				pixel = me.bottom - (me.height / range * (rightValue - start));
 			}
-
-			pixel = me.bottom - (me.height / range * (rightValue - start));
-			return Math.round(pixel);
+			return pixel;
 		},
 		getValueForPixel: function(pixel) {
 			var me = this;

test/specs/core.controller.tests.js

@@ -759,8 +759,8 @@ describe('Chart', function() {
 
 			// Verify that points are at their initial correct location,
 			// then we will reset and see that they moved
-			expect(meta.data[0]._model.y).toBe(333);
-			expect(meta.data[1]._model.y).toBe(183);
+			expect(meta.data[0]._model.y).toBeCloseToPixel(333);
+			expect(meta.data[1]._model.y).toBeCloseToPixel(183);
 			expect(meta.data[2]._model.y).toBe(32);
 			expect(meta.data[3]._model.y).toBe(484);
 

test/specs/core.tooltip.tests.js

@@ -764,7 +764,7 @@ describe('Core.Tooltip', function() {
 
 	it('Should not update if active element has not changed', function() {
 		var chart = window.acquireChart({
-			type: 'bar',
+			type: 'line',
 			data: {
 				datasets: [{
 					label: 'Dataset 1',