**Do you want to request a *feature* or report a *bug*?**
bug

**What is the current behavior?**
If there is a client/server mismatch for text inside of an a or button element, it causes it to be automatically focused on page load.

**If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem via https://jsfiddle.net or similar (template for React 16: https://jsfiddle.net/Luktwrdm/, template for React 15: https://jsfiddle.net/hmbg7e9w/).**
```
let text;
let URL = '/randomURL';
if (typeof window !== 'undefined') {
  text = 'CLIENT TEXT';
} else {
  text = 'TEXT';
}

return (
  <a href={URL}>
    {text}
  </a>
);
```

if the focus is not on the window (i.e. if a dom element is selected in the chrome inspector or react inspector widnow), then it doesn't add the focus.

**What is the expected behavior?**
The expected behavior is that it would either show CLIENT TEXT or TEXT (depending on how React16 resolves the diff), but for it not to be automatically highlighted 

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
React16 / macosx / chrome + ff + safari
expect(() => {
      ReactDOMServer.renderToString(
        <div>{ReactDOM.createPortal(<div />, div)}</div>,
      );
    }).toThrow(
      'Portals are not currently supported by the server renderer. ' +
        'Render them conditionally so that they only appear on the client render.',
    );
  });
  it('should throw rendering call/return on the server', () => {
    const div = document.createElement('div');
    expect(() => {
      ReactDOMServer.renderToString(
        <div>{ReactCallReturn.unstable_createReturn(42)}</div>,
      );
    }).toThrow(
      'The experimental Call and Return types are not currently supported by the server renderer.',
    );
    expect(() => {
      ReactDOMServer.renderToString(
        <div>
          {ReactCallReturn.unstable_createCall(null, function() {}, {})}
        </div>,
      );
    }).toThrow(
      'The experimental Call and Return types are not currently supported by the server renderer.',
    );
  });
});