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(customElement.getAttribute('foo')).toBe('one');
      
      Object.defineProperty(customElement, 'foo', {
        set: function(x) {
          this._foo = x;
        },
        get: function() {
          return this._foo;
        },
      });
      ReactDOM.render(<my-custom-element foo="two" />, container);
      expect(customElement.foo).toBe('two');
      expect(customElement.getAttribute('foo')).toBe('one');
    });
    
    it('custom element properties should accept functions', () => {
      const container = document.createElement('div');
      document.body.appendChild(container);
      ReactDOM.render(<my-custom-element />, container);
      const customElement = container.querySelector('my-custom-element');
      
      Object.defineProperty(customElement, 'foo', {
        set: function(x) {
          this._foo = x;
        },
        get: function() {
          return this._foo;
        },
      });
      function myFunction() {