Allow Effen Styles to be extendable

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1006053002

examples/stocks-fn/stockarrow.dart

@@ -74,11 +74,11 @@ class StockArrow extends Component {
 
     return new Container(
       inlineStyle: 'border-color: $border',
-      styles: [_style],
+      style: _style,
       children: [
         new Container(
           inlineStyle: 'border-$type-color: $border',
-          styles: [up ? _upStyle : _downStyle]
+          style: up ? _upStyle : _downStyle
         )
       ]
     );

examples/stocks-fn/stockrow.dart

@@ -47,23 +47,23 @@ class StockRow extends Component {
       ),
       new Container(
         key: 'Ticker',
-        styles: [_tickerStyle],
+        style: _tickerStyle,
         children: [new Text(stock.symbol)]
       ),
       new Container(
         key: 'LastSale',
-        styles: [_lastSaleStyle],
+        style: _lastSaleStyle,
         children: [new Text(lastSale)]
       ),
       new Container(
         key: 'Change',
-        styles: [_changeStyle],
+        style: _changeStyle,
         children: [new Text(changeInPrice)]
       )
     ];
 
     return new Material(
-      styles: [_style],
+      style: _style,
       children: children
     );
   }

examples/stocks-fn/stocksapp.dart

@@ -105,19 +105,19 @@ class StocksApp extends App {
 
     var toolbar = new Toolbar(
       children: [
-        new Icon(key: 'menu', styles: [_iconStyle],
+        new Icon(key: 'menu', style: _iconStyle,
             size: 24,
             type: 'navigation/menu_white')
           ..events.listen('click', _drawerAnimation.toggle),
         new Container(
-          styles: [_titleStyle],
+          style: _titleStyle,
           children: [title]
         ),
-        new Icon(key: 'search', styles: [_iconStyle],
+        new Icon(key: 'search', style: _iconStyle,
             size: 24,
             type: 'action/search_white')
           ..events.listen('click', _handleSearchClick),
-        new Icon(key: 'more_white', styles: [_iconStyle],
+        new Icon(key: 'more_white', style: _iconStyle,
             size: 24,
             type: 'navigation/more_vert_white')
       ]
@@ -133,7 +133,7 @@ class StocksApp extends App {
       children: [
         new Container(
           key: 'Content',
-          styles: [_style],
+          style: _style,
           children: [toolbar, list]
         ),
         fab,