Better check for feature using mixin

ee/app/assets/javascripts/burndown_chart/components/burn_charts.vue

 <script>
 import { GlButton, GlButtonGroup } from '@gitlab/ui';
+import glFeatureFlagsMixin from '~/vue_shared/mixins/gl_feature_flags_mixin';
 import { __ } from '~/locale';
 import BurndownChart from './burndown_chart.vue';
 
@@ -9,6 +10,7 @@ export default {
     GlButtonGroup,
     BurndownChart,
   },
+  mixins: [glFeatureFlagsMixin()],
   props: {
     startDate: {
       type: String,
@@ -32,12 +34,11 @@ export default {
   data() {
     return {
       issuesSelected: true,
-      burnupChartsEnabled: gon.features.burnupCharts,
     };
   },
   computed: {
     title() {
-      return this.burnupChartsEnabled ? __('Charts') : __('Burndown chart');
+      return this.glFeatures.burnupCharts ? __('Charts') : __('Burndown chart');
     },
     issueButtonCategory() {
       return this.issuesSelected ? 'primary' : 'secondary';
@@ -47,11 +48,8 @@ export default {
     },
   },
   methods: {
-    showIssueCount() {
-      this.issuesSelected = true;
-    },
-    showIssueWeight() {
-      this.issuesSelected = false;
+    setIssueSelected(selected) {
+      this.issuesSelected = selected;
     },
   },
 };
@@ -67,7 +65,7 @@ export default {
           :category="issueButtonCategory"
           variant="info"
           size="small"
-          @click="showIssueCount"
+          @click="setIssueSelected(true)"
         >
           {{ __('Issues') }}
         </gl-button>
@@ -77,13 +75,13 @@ export default {
           variant="info"
           size="small"
           data-qa-selector="weight_button"
-          @click="showIssueWeight"
+          @click="setIssueSelected(false)"
         >
           {{ __('Issue weight') }}
         </gl-button>
       </gl-button-group>
     </div>
-    <div v-if="burnupChartsEnabled" class="row">
+    <div v-if="glFeatures.burnupCharts" class="row">
       <burndown-chart
         :start-date="startDate"
         :due-date="dueDate"

ee/spec/frontend/burndown_chart/components/burn_charts_spec.js

@@ -20,30 +20,18 @@ describe('burndown_chart', () => {
     openIssuesWeight: [],
   };
 
-  const createComponent = (props = {}) => {
+  const createComponent = ({ props = {}, featureEnabled = false } = {}) => {
     wrapper = shallowMount(BurnCharts, {
       propsData: {
         ...defaultProps,
         ...props,
       },
+      provide: {
+        glFeatures: { burnupCharts: featureEnabled },
+      },
     });
   };
 
-  let origProp;
-
-  beforeEach(() => {
-    origProp = window.gon;
-    window.gon = {
-      features: {
-        burnupCharts: false,
-      },
-    };
-  });
-
-  afterEach(() => {
-    window.gon = origProp;
-  });
-
   it('includes Issues and Issue weight buttons', () => {
     createComponent();
 
@@ -80,9 +68,7 @@ describe('burndown_chart', () => {
 
   describe('feature disabled', () => {
     beforeEach(() => {
-      window.gon.features.burnupCharts = false;
-
-      createComponent();
+      createComponent({ featureEnabled: false });
     });
 
     it('does not reduce width of burndown chart', () => {
@@ -97,9 +83,7 @@ describe('burndown_chart', () => {
 
   describe('feature enabled', () => {
     beforeEach(() => {
-      window.gon.features.burnupCharts = true;
-
-      createComponent();
+      createComponent({ featureEnabled: true });
     });
 
     it('reduces width of burndown chart', () => {