Add a simple initial-render benchmark test case

.eslintignore

@@ -11,4 +11,5 @@ docs/vendor/bundle/
 examples/
 # Ignore built files.
 build/
+scripts/bench/bench-*.js
 vendor/react-dom.js

scripts/bench/README.md

@@ -0,0 +1,23 @@
+Work-in-progress benchmarks.
+
+## Running one
+One thing you can do with them is benchmark initial render time for a realistic hierarchy:
+
+```
+$ which jsc
+/System/Library/Frameworks/JavaScriptCore.framework/Versions/Current/Resources/jsc
+$ jsc react-0.14.0.min.js bench-pe-es5.js -e 'var START=Date.now(); React.renderToString(React.createElement(Benchmark)); var END=Date.now(); print(END-START);'
+45
+```
+
+Substitute `js` or `v8` for `jsc` to use SpiderMonkey or V8, respectively, if you've installed them.
+
+## Creating one
+
+To create one, copy `extract-component.js` to your clipboard and paste it into the Chrome console on facebook.com, perhaps after changing the root ID if you don't want the tree with ID `.0`.
+
+Then to convert it to ES5:
+
+```
+babel --whitelist react,react.displayName --compact false bench-pe.js >bench-pe-es5.js
+```