Observed this on react@16.0.0-beta.5

```js
import React from 'react';
import { renderToString } from 'react-dom/server';

const B = () => 'b';

console.log(renderToString(<div>{'a'}<B />{'c'}</div>));
```

This renders as `<div data-reactroot="">a<!-- -->bc</div>`. If you try to hydrate this you'll get the error: Text content did not match. Server: "bc" Client: "b".
var setCurrentDebugStack = function(stack) {
    currentDebugElementStack = stack[stack.length - 1].debugElementStack;
    
    currentDebugElementStack.length = 0;
    currentDebugStack = stack;
    ReactDebugCurrentFrame.getCurrentStack = getStackAddendum;
  };
  var pushElementToDebugStack = function(element) {
    if (currentDebugElementStack !== null) {
      currentDebugElementStack.push(element);
    }
  };
  var resetCurrentDebugStack = function() {
    currentDebugElementStack = null;
    currentDebugStack = null;
    ReactDebugCurrentFrame.getCurrentStack = null;
  };
  var getStackAddendum = function(): null | string {
    if (currentDebugStack === null) {
      return null;
    }
    let stack = '';
    let debugStack = currentDebugStack;
    for (let i = debugStack.length - 1; i >= 0; i--) {
      let debugElementStack = debugStack[i].debugElementStack;
      for (let ii = debugElementStack.length - 1; ii >= 0; ii--) {
        stack += describeStackFrame(debugElementStack[ii]);
      }
    }
    return stack;