Material light and dark themes for Sky widgets

sky/sdk/lib/theme/theme_data.dart

Index: sky/sdk/lib/theme/theme_data.dart
diff --git a/sky/sdk/lib/theme/theme_data.dart b/sky/sdk/lib/theme/theme_data.dart
index f5873978d49ff311f1c059d6dbd377a6f9021b30..7b06afc67ed08ea9eb7aae67ce1fc88ad9511408 100644
--- a/sky/sdk/lib/theme/theme_data.dart
+++ b/sky/sdk/lib/theme/theme_data.dart
@@ -4,10 +4,38 @@
 
 import 'dart:sky';
 
-import 'typography.dart';
+import 'typography.dart' as typography;
+import 'colors.dart' as colors;
 
 class ThemeData {
-  const ThemeData({ this.text, this.color });
-  final TextTheme text;
-  final Map<int, Color> color;
+
+  ThemeData.light({
+    this.primary,
+    this.accent,
+    bool darkToolbar: false })
+    : toolbarText = darkToolbar ? typography.white : typography.black,
+      text = typography.black,
+      backgroundColor = colors.Grey[50],
+      dialogColor = colors.White;
+
+  ThemeData.dark({ this.primary, this.accent })
+    : toolbarText = typography.white,
+      text = typography.white,
+      backgroundColor = colors.Grey[850],
+      dialogColor = colors.Grey[800];
+
+  ThemeData.fallback()
+    : primary = colors.Indigo,
+      accent = colors.PinkAccent,
+      toolbarText = typography.white,
+      text = typography.black,
+      backgroundColor = colors.Grey[50],
+      dialogColor = colors.White;
+
+  final Map<int, Color> primary;
+  final Map<int, Color> accent;
+  final typography.TextTheme text;
+  final typography.TextTheme toolbarText;
+  final Color backgroundColor;
+  final Color dialogColor;
 }