**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
warnForDeletedHydratableText,
  warnForInsertedHydratedElement,
  warnForInsertedHydratedText,
} = ReactDOMFiberComponent;
const {updatedAncestorInfo} = validateDOMNesting;
const {precacheFiberNode, updateFiberProps} = ReactDOMComponentTree;
let SUPPRESS_HYDRATION_WARNING;
let topLevelUpdateWarnings;
let warnOnInvalidCallback;
if (__DEV__) {
  SUPPRESS_HYDRATION_WARNING = 'suppressHydrationWarning';
  if (
    typeof Map !== 'function' ||
    Map.prototype == null ||
    typeof Map.prototype.forEach !== 'function' ||
    typeof Set !== 'function' ||
    Set.prototype == null ||
    typeof Set.prototype.clear !== 'function' ||
    typeof Set.prototype.forEach !== 'function'
  ) {
    warning(
      false,
      'React depends on Map and Set built-in types. Make sure that you load a ' +
        'polyfill in older browsers. https://fb.me/react-polyfills',
    );
  }
  topLevelUpdateWarnings = (container: DOMContainer) => {
    if (__DEV__) {
      if (
        container._reactRootContainer &&