**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
const isContainerReactRoot =
          container.nodeType === 1 &&
          isValidContainer(container.parentNode) &&
          !!container.parentNode._reactRootContainer;
        warning(
          !hasNonRootReactChild,
          "unmountComponentAtNode(): The node you're attempting to unmount " +
            'was rendered by React and is not a top-level container. %s',
          isContainerReactRoot
            ? 'You may have accidentally passed in a React root node instead ' +
              'of its container.'
            : 'Instead, have the parent component update its state and ' +
              'rerender in order to remove this component.',
        );
      }
      return false;
    }
  },
  
  
  unstable_createPortal: createPortal,
  unstable_batchedUpdates: ReactGenericBatching.batchedUpdates,
  unstable_deferredUpdates: DOMRenderer.deferredUpdates,
  flushSync: DOMRenderer.flushSync,
  __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED: {
    
    EventPluginHub,
    
    EventPluginRegistry,
    EventPropagators,