Allow scale to auto-adjust it's min when stacked (#9045)

Author: kurkle

src/scales/scale.linearbase.js

@@ -168,14 +168,14 @@ export default class LinearScaleBase extends Scale {
 
   handleTickRangeOptions() {
     const me = this;
-    const {beginAtZero, stacked} = me.options;
+    const {beginAtZero} = me.options;
     const {minDefined, maxDefined} = me.getUserBounds();
     let {min, max} = me;
 
     const setMin = v => (min = minDefined ? min : v);
     const setMax = v => (max = maxDefined ? max : v);
 
-    if (beginAtZero || stacked) {
+    if (beginAtZero) {
       const minSign = sign(min);
       const maxSign = sign(max);
 

test/specs/scale.linear.tests.js

@@ -194,6 +194,12 @@ describe('Linear Scale', function() {
     chart.scales.y.options.stacked = true;
     chart.update();
 
+    expect(chart.scales.y.min).toBe(30);
+    expect(chart.scales.y.max).toBe(90);
+
+    chart.scales.y.options.beginAtZero = true;
+    chart.update();
+
     expect(chart.scales.y.min).toBe(0);
     expect(chart.scales.y.max).toBe(90);
   });