Update Sky widgets to have more material design

sky/examples/widgets/widget-root.sky

 <!--
 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 -->
 <import src="/sky/framework/sky-box.sky" />
 <import src="/sky/framework/sky-button.sky" />
 <import src="/sky/framework/sky-checkbox.sky" />
 <import src="/sky/framework/sky-element.sky" />
 <import src="/sky/framework/sky-input.sky" />
 <import src="/sky/framework/sky-radio.sky" />
 <import src="/sky/framework/sky-scrollable.sky" />
 <sky-element>
 <template>
   <style>
+  :host {
+    font-family: 'Roboto Regular', 'Helvetica';
+  }
   div {
     display: flex;
     align-items: center;
   }
   sky-checkbox {
     margin: 5px;
   }
   .output {
     margin-left: 48px;
   }
   sky-scrollable {
     height: -webkit-fill-available;
   }
   </style>
   <sky-scrollable>
     <sky-box title='Text'>
       <sky-input id="text" value="{{ inputValue }}" />
       <div>value = {{ inputValue }}</div>
     </sky-box>
   
     <sky-box title='Buttons'>
-      <sky-button id='button'>Button</sky-button>
-      <div>highlight: {{ myButton.highlight }}</div>
-      <div>clickCount: {{ clickCount }}</div>
+      <div style="display: flex; flex-direction: horizontal">
+        <div style="flex:1" />
+        <sky-button level="1" id="button">CANCEL</sky-button>
+        <sky-button level="1" primary>CONFIRM</sky-button>
+      </div>
     </sky-box>
   
     <sky-box title='Checkboxes'>
       <div><sky-checkbox id='checkbox' checked='{{ checked }}'/>Checkbox</div>
       <div class="output">highlight: {{ myCheckbox.highlight }}</div>
       <div class="output">checked: {{ myCheckbox.checked }}</div>
       <div><sky-checkbox id='checkbox' checked="true"/>Checkbox, default checked.</div>
       <div class="output">checked: {{ checked }}</div>
     </sky-box>
   
@@ skipping 34 matching lines @@
   void _handleClick(_) {
     _clickCount++;
     _checked = !_checked;
     _inputValue = "Moar clicking ${_clickCount}";
   }
 }
 
 _init(script) => register(script, WidgetRoot);
 </script>
 </sky-element>