Re-configured samples page.

src/site/samples/raf/index.markdown

Index: src/site/samples/raf/index.markdown
diff --git a/src/site/samples/raf/index.markdown b/src/site/samples/raf/index.markdown
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+---
+layout: default
+title: Leaner, Meaner, Faster Animations with requestAnimationFrame
+live_example_url: /samples/raf/example/index.html
+header:
+  css: ["/samples/samples.css"]
+---
+
+## {{ page.title }}
+
+This sample ports the example used in
+[this HTML5Rocks article](http://www.html5rocks.com/en/tutorials/speed/animations/)
+by Paul Lewis about correctly using requestAnimationFrame for your animations.
+
+Use the up and down keys on your keyboard to activate the animation.
+
+Read the
+[source](https://github.com/dart-lang/dart-samples/tree/master/web/html5/speed/animations).
+
+<iframe class="running-app-frame"
+        style="height:400px;width:100%;"
+        src="{{page.live_example_url}}">
+</iframe>
+
+See all [samples](/samples/)