Revert "Merge pull request #6431 from sebmarkbage/killspread"

This reverts commit a37e4e94fc, reversing
changes made to 411951d5b8.

src/isomorphic/React.js

@@ -65,6 +65,9 @@ var React = {
   DOM: ReactDOMFactories,
 
   version: ReactVersion,
+
+  // Hook for JSX spread, don't use this for anything else.
+  __spread: Object.assign,
 };
 
 module.exports = React;