Add a confirmation dialog to stock app Settings page and style it by default

sky/sdk/lib/widgets/dialog.dart

 // 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 '../theme/colors.dart' as colors;
 import 'basic.dart';
+import 'default_text_style.dart';
 import 'material.dart';
 import "theme.dart";
 
 class Dialog extends Component {
   Dialog({
     String key,
     this.title,
     this.content,
     this.actions,
     this.onDismiss
   }) : super(key: key);
 
   final Widget title;
   final Widget content;
-  final Widget actions;
+  final List<Widget> actions;
   final Function onDismiss;
 
   Color get color {
     switch (Theme.of(this).brightness) {
       case ThemeBrightness.light:
         return colors.White;
       case ThemeBrightness.dark:
         return colors.Grey[800];
     }
   }
 
   Widget build() {
     Container mask = new Container(
       decoration: const BoxDecoration(
         backgroundColor: const Color(0x7F000000)));
 
     List<Widget> children = new List<Widget>();
 
-    if (title != null)
-      children.add(title);
+    if (title != null) {
+      children.add(new Padding(
+        padding: new EdgeDims(24.0, 24.0, content == null ? 20.0 : 0.0, 24.0),
+        child: new DefaultTextStyle(
+          style: Theme.of(this).text.title,
+          child: title
+        )
+      ));
+    }
 
-    if (content != null)
-      children.add(content);
+    if (content != null) {
+      children.add(new Padding(
+        padding: const EdgeDims(20.0, 24.0, 24.0, 24.0),
+        child: new DefaultTextStyle(
+          style: Theme.of(this).text.subhead,
+          child: content
+        )
+      ));
+    }
 
     if (actions != null)
-      children.add(actions);
+      children.add(new Flex(actions, justifyContent: FlexJustifyContent.flexEnd));
 
     return new Stack([
       new Listener(
         child: mask,
         onGestureTap: (_) => onDismiss()
       ),
       new Center(
-        child: new ConstrainedBox(
-          constraints: new BoxConstraints(minWidth: 280.0),
-          child: new Material(
-            level: 4,
-            color: color,
-            child: new ShrinkWrapWidth(
-              child: new Block(children)
+        child: new Container(
+          margin: new EdgeDims.symmetric(horizontal: 40.0, vertical: 24.0),
+          child: new ConstrainedBox(
+            constraints: new BoxConstraints(minWidth: 280.0),
+            child: new Material(
+              level: 4,
+              color: color,
+              child: new ShrinkWrapWidth(
+                child: new Block(children)
+              )
             )
           )
         )
       )
     ]);
   }
 }