Move example fn widgets into sky/framework/components

sky/examples/fn/widgets/checkbox.dart

Index: sky/examples/fn/widgets/checkbox.dart
diff --git a/sky/examples/fn/widgets/checkbox.dart b/sky/examples/fn/widgets/checkbox.dart
deleted file mode 100644
index aa76471e014679af2469af1dd373da8cd0438278..0000000000000000000000000000000000000000
--- a/sky/examples/fn/widgets/checkbox.dart
+++ /dev/null
@@ -1,77 +0,0 @@
-part of widgets;
-
-class Checkbox extends ButtonBase {
-
-  bool checked;
-  ValueChanged onChanged;
-
-  static Style _style = new Style('''
-    transform: translateX(0);
-    display: flex;
-    justify-content: center;
-    align-items: center;
-    -webkit-user-select: none;
-    cursor: pointer;
-    width: 30px;
-    height: 30px;'''
-  );
-
-  static Style _containerStyle = new Style('''
-    border: solid 2px;
-    border-color: rgba(90, 90, 90, 0.25);
-    width: 10px;
-    height: 10px;'''
-  );
-
-  static Style _containerHighlightStyle = new Style('''
-    border: solid 2px;
-    border-color: rgba(90, 90, 90, 0.25);
-    width: 10px;
-    height: 10px;
-    border-radius: 10px;
-    background-color: orange;
-    border-color: orange;'''
-  );
-
-  static Style _uncheckedStyle = new Style('''
-    top: 0px;
-    left: 0px;'''
-  );
-
-  static Style _checkedStyle = new Style('''
-    top: 0px;
-    left: 0px;
-    transform: translate(2px, -15px) rotate(45deg);
-    width: 10px;
-    height: 20px;
-    border-style: solid;
-    border-top: none;
-    border-left: none;
-    border-right-width: 2px;
-    border-bottom-width: 2px;
-    border-color: #0f9d58;'''
-  );
-
-  Checkbox({ Object key, this.onChanged, this.checked }) : super(key: key);
-
-  Node build() {
-    return new Container(
-      style: _style,
-      children: [
-        super.build(),
-        new Container(
-          style: _highlight ? _containerHighlightStyle : _containerStyle,
-          children: [
-            new Container(
-              style: checked ? _checkedStyle : _uncheckedStyle
-            )
-          ]
-        )
-      ]
-    )..events.listen('click', _handleClick);
-  }
-
-  void _handleClick(sky.Event e) {
-    onChanged(!checked);
-  }
-}