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?
itRenders('boolean prop with object value', async render => {
        const e = await render(<div hidden={{foo: 'bar'}} />);
        expect(e.getAttribute('hidden')).toBe('');
      });
      
      itRenders('boolean prop with non-zero number value', async render => {
        const e = await render(<div hidden={10} />);
        expect(e.getAttribute('hidden')).toBe('');
      });
      
      itRenders('boolean prop with zero value', async render => {
        const e = await render(<div hidden={0} />);
        expect(e.getAttribute('hidden')).toBe(null);
      });
      itRenders('no boolean prop with null value', async render => {
        const e = await render(<div hidden={null} />);
        expect(e.hasAttribute('hidden')).toBe(false);
      });
      itRenders('no boolean prop with function value', async render => {
        const e = await render(<div hidden={function() {}} />, 1);
        expect(e.hasAttribute('hidden')).toBe(false);
      });
      itRenders('no boolean prop with symbol value', async render => {
        const e = await render(<div hidden={Symbol('foo')} />, 1);
        expect(e.hasAttribute('hidden')).toBe(false);
      });
    });
    describe('download property (combined boolean/string attribute)', function() {
      itRenders('download prop with true value', async render => {