introduce web_components pkg for consolidated polyfills

samples/third_party/todomvc/web/app/app.css

 /* base.css overrides */
 
 html,
 body {
   margin: 0;
   padding: 0;
 }
 
 body {
   font: 14px 'Helvetica Neue', Helvetica, Arial, sans-serif;
   line-height: 1.4em;
   background: #eaeaea url('bg.png');
   color: #4d4d4d;
   width: 550px;
   margin: 0 auto;
   -webkit-font-smoothing: antialiased;
   -moz-font-smoothing: antialiased;
   -ms-font-smoothing: antialiased;
   -o-font-smoothing: antialiased;
-  /* font-smoothing: antialiased; */
+  font-smoothing: antialiased;

[Jennifer Messerly, 2014/02/08 01:13:29]

I updated TodoMVC's CSS file

[Siggi Cherem (dart-lang), 2014/02/10 20:49:23]

why were we commenting these out? were we getting warnings on some browsers?

[Jennifer Messerly, 2014/02/10 22:17:11]

ah, probably! Still, that isn't a good reason :)

 }
 
 body > header {
   padding-top: 22px;
   margin-bottom: -5px;
 }
 
 h1 {
   /*  position: absolute;
   top: -120px;*/
   width: 100%;
   font-size: 70px;
   font-weight: bold;
   text-align: center;
   color: #b3b3b3;
   color: rgba(255, 255, 255, 0.3);
   text-shadow: -1px -1px rgba(0, 0, 0, 0.2);
-  /* -webkit-text-rendering: optimizeLegibility; */
+  -webkit-text-rendering: optimizeLegibility;
   -moz-text-rendering: optimizeLegibility;
   -ms-text-rendering: optimizeLegibility;
   -o-text-rendering: optimizeLegibility;
   text-rendering: optimizeLegibility;
 }
 
 #info {
   margin: 65px auto 0;
   color: #a6a6a6;
   font-size: 12px;
@@ skipping 147 matching lines @@
     width: auto;
     margin: 0 0 0 300px;
   }
   /**body*/.learn-bar > .learn {
     left: 8px;
   }
   /**body*/.learn-bar #todoapp {
     width: 550px;
     margin: 130px auto 40px auto;
   }
-}
+}