canvas tests

• tracks HTMLCanvasElement ‣

  TypeError: Cannot read properties of undefined (reading 'skip')
      at testCanvas (https://greggman.github.io/webgpu-memory/test/tests/canvas-tests.js:19:12)
      at async Context.<anonymous> (https://greggman.github.io/webgpu-memory/test/tests/canvas-tests.js:107:5)

  async function() {
      const canvas1 = document.createElement('canvas');
      const canvas2 = document.createElement('canvas');
      await testCanvas(canvas1, canvas2);
    }