samples/poppopwin: upgrade to first-class sample

samples/pop_pop_win/web/index.html

Index: samples/pop_pop_win/web/index.html
diff --git a/samples/third_party/pop-pop-win/web/index.html b/samples/pop_pop_win/web/index.html
similarity index 79%
rename from samples/third_party/pop-pop-win/web/index.html
rename to samples/pop_pop_win/web/index.html
index 25fd846533e23b28aa539dbe330f0427e04eba62..858680a4e0fa319202256c986f1726937c17bdba 100644
--- a/samples/third_party/pop-pop-win/web/index.html
+++ b/samples/pop_pop_win/web/index.html
@@ -4,7 +4,7 @@
     <title>Pop, Pop, Win!</title>
     <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
     <link rel="shortcut icon" href="favicon.ico" />
-    <link rel='stylesheet' type='text/css' href='style.css' />
+    <link rel='stylesheet' type='text/css' href='assets/poppopwin/style.css' />
     <link href='http://fonts.googleapis.com/css?family=Josefin+Sans:400,700|Slackey' rel='stylesheet' type='text/css'>
     <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no" />
     <meta property="og:title" content="Pop, Pop, Win!" />
@@ -31,28 +31,17 @@
       </div>
       <div id='help'>
         <h1>Help</h1>
-        <img src='images/help-surround.jpg'>
+        <img src='assets/poppopwin/images/help-surround.jpg'>
         <p>Click on balloons to pop them.</p>
         <p>A revealed number tells you how many bombs are next to that square.</p>
         <p>The count includes squares above, below, left, right and diagonal.</p>
         <p><em>One of these balloons is a bomb. Can you guess which one?</em></p>
-        <img src='images/help-freeze.jpg'>
+        <img src='assets/poppopwin/images/help-freeze.jpg'>
         <p>If you're certain a balloon is hiding a bomb, freeze it.</p>
         <p>Freeze a balloon by holding down the shift key and clicking.</p>
         <p>Every time you freeze a balloon, the bomb count goes down.</p>
         <p>Unfreeze a balloon the same way: shift-click.</p>
       </div>
     </div>
-
-    <script>
-      (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
-      (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
-      m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
-      })(window,document,'script','//www.google-analytics.com/analytics.js','ga');
-
-      ga('create', 'UA-3441863-10', 'dart-lang.github.io');
-      ga('send', 'pageview');
-
-    </script>
   </body>
 </html>