When setting boolean attributes on Web Components
`<x-search somebool name={this.props.name} />`
they get rendered as attribute/value pairs instead
`<x-search somebool="true" name={this.props.name}>`

This causes problems with some AMP components, for eg. `<amp-iframe />` which has a `resizable` attribute that gets rendered as `resizable="true"`. This results in non valid AMP content and developers crying with blood tears on their keyboards :)
> The attribute 'resizable' in tag 'amp-iframe' is set to the invalid value 'true'. (see https://www.ampproject.org/docs/reference/components/amp-iframe)

Is there any reason for the current behaviour? Will changing this break something else?
expect(container.firstChild.onunknown).toBe(undefined);
      expect(() =>
        ReactDOM.render(<div on-unknown='alert("hack")' />, container),
      ).toErrorDev(
        'Warning: Unknown event handler property `on-unknown`. It will be ignored.\n    in div (at **)',
      );
      expect(container.firstChild.hasAttribute('on-unknown')).toBe(false);
      expect(container.firstChild['on-unknown']).toBe(undefined);
    });
    it('should warn for unknown function event handlers', () => {
      const container = document.createElement('div');
      expect(() =>
        ReactDOM.render(<div onUnknown={function() {}} />, container),
      ).toErrorDev(
        'Warning: Unknown event handler property `onUnknown`. It will be ignored.\n    in div (at **)',
      );
      expect(container.firstChild.hasAttribute('onUnknown')).toBe(false);
      expect(container.firstChild.onUnknown).toBe(undefined);
      expect(() =>
        ReactDOM.render(<div onunknown={function() {}} />, container),
      ).toErrorDev(
        'Warning: Unknown event handler property `onunknown`. It will be ignored.\n    in div (at **)',
      );
      expect(container.firstChild.hasAttribute('onunknown')).toBe(false);
      expect(container.firstChild.onunknown).toBe(undefined);
      expect(() =>
        ReactDOM.render(<div on-unknown={function() {}} />, container),
      ).toErrorDev(
        'Warning: Unknown event handler property `on-unknown`. It will be ignored.\n    in div (at **)',
      );