Re-configured samples page.

src/site/samples/stopwatch/index.markdown

+---
+layout: default
+title: Defining a custom element
+live_example_url: /docs/tutorials/polymer-intro/examples/stopwatch/out/web/index.html
+header:
+  css: ["/samples/samples.css"]
+---
+
+## {{ page.title }}
+
+Start and stop the stopwatch. Reset the stopwatch to 00:00 using the Reset
+button.
+
+This example shows how to implement a custom element using Polymer.
+
+In this example, the stopwatch is a custom element. The definition of a custom
+element encapsulates and hides the implementation details. With custom
+elements, you can easily create new kinds of elements that have semantically
+meaningful tags and that are easy to share, reuse, and read. For example, to
+put a stopwatch element on the page, you write:
+
+`<tute-stopwatch></tute-stopwatch>`
+
+The counting text is a String in Dart that changes dynamically based on a
+Timer. Polymer’s one-way data binding feature keeps the UI in sync with the
+data as it changes.
+
+Declarative event handler binding lets you set up event handlers for UI
+elements on the HTML-side.
+
+Read this [tutorial](/docs/tutorials/polymer-intro) for
+more detail, or read the
+[source](https://github.com/dart-lang/dart-tutorials-samples/tree/master/web/stopwatch).
+
+
+<iframe class="running-app-frame"
+        style="height:300px;width:300px;"
+        src="{{page.live_example_url}}">
+</iframe>
+
+See all [samples](/samples/)