It seems problematic to allow arbitary non-lowercase attribute on HTML nodes. Because the server has no ability to keep them case sensitive (HTML isn't). So they will end up different on the client.

We should probably warn if the attribute is not a known one *and* is not lowercase.
expectDev(console.error.calls.argsFor(0)[0]).toEqual(
        'Warning: `NaN` is an invalid value for the `fontSize` css style property.',
      );
    });
    it('should update styles if initially null', () => {
      var styles = null;
      var container = document.createElement('div');
      ReactDOM.render(<div style={styles} />, container);
      var stubStyle = container.firstChild.style;
      styles = {display: 'block'};
      ReactDOM.render(<div style={styles} />, container);
      expect(stubStyle.display).toEqual('block');
    });
    it('should update styles if updated to null multiple times', () => {
      var styles = null;
      var container = document.createElement('div');
      ReactDOM.render(<div style={styles} />, container);
      styles = {display: 'block'};
      var stubStyle = container.firstChild.style;
      ReactDOM.render(<div style={styles} />, container);
      expect(stubStyle.display).toEqual('block');
      ReactDOM.render(<div style={null} />, container);
      expect(stubStyle.display).toEqual('');
      ReactDOM.render(<div style={styles} />, container);
      expect(stubStyle.display).toEqual('block');
      ReactDOM.render(<div style={null} />, container);
      expect(stubStyle.display).toEqual('');
    });
    it('should allow named slot projection on both web components and regular DOM elements', () => {
      var container = document.createElement('div');