This adds `{Page,Frame}.isChecked(selector)` and `ElementHandle.isChecked()` methods.
Useful to do assertions in tests:
```js
await page.click('text="Add TODO"');
expect(await page.isChecked('.item-done')).toBe(false);
```
These methods are useful for verification in tests, e.g.
```js
expect(await page.isEnabled(':text("Remove All")')).toBe(false);
await page.click(':text("Add Item")');
expect(await page.isVisible('.item:text("new item")')).toBe(true);
expect(await page.isEnabled(':text("Remove All")')).toBe(true);
```
- Fill and click actions pass metadata to Progress.
- Progress reports success/failure through instrumentation.
- Tracer consumes ActionResult and ActionMetadata and records them.
Currently, only click and fill actions pass metadata to
contain the size of the change. Everything else should follow.
