feat(g-canvas): 增加 antvis#726 bug单测

packages/g-canvas/tests/bugs/issue-726-spec.js

@@ -0,0 +1,27 @@
+const expect = require('chai').expect;
+import { Canvas } from '../../src';
+const container = document.createElement('canvas');
+document.body.appendChild(container);
+
+describe('#726', () => {
+  it('Total canvas memory use exceeds xxxMB bug', () => {
+    const canvas = new Canvas({
+      container,
+      width: 600,
+      height: 500,
+    });
+
+    const canvasEl = canvas.get('el');
+    const pixelRatio = canvas.getPixelRatio();
+
+    expect(canvasEl.width).eql(600 * pixelRatio);
+    expect(canvasEl.height).eql(500 * pixelRatio);
+
+    canvas.destroy();
+
+    // 销毁canvas后需要设置宽高为0
+    // 解决ios场景下 canvas无法进行垃圾回收的问题
+    expect(canvasEl.width).eql(0);
+    expect(canvasEl.height).eql(0);
+  });
+});