Remove Material's opinion about background colours, since in fact the background colour varies dram…

sky/sdk/lib/widgets/material.dart

Index: sky/sdk/lib/widgets/material.dart
diff --git a/sky/sdk/lib/widgets/material.dart b/sky/sdk/lib/widgets/material.dart
index 527e055bde83a96951d3e262e55f0aa86ed23c13..793fe9606634c5353c7cf89ba16f87298c9c5ad5 100644
--- a/sky/sdk/lib/widgets/material.dart
+++ b/sky/sdk/lib/widgets/material.dart
@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 
 import '../painting/box_painter.dart';
-import '../theme/colors.dart' as colors;
 import '../theme/edges.dart';
 import '../theme/shadows.dart';
 import 'basic.dart';
@@ -27,17 +26,6 @@ class Material extends Component {
   final MaterialEdge edge;
   final Color color;
 
-  Color get backgroundColor {
-    if (color != null)
-      return color;
-    switch (Theme.of(this).brightness) {
-      case ThemeBrightness.light:
-        return colors.Grey[50];
-      case ThemeBrightness.dark:
-        return colors.Grey[850];
-    }
-  }
-
   // TODO(ianh): we should make this animate level changes and color changes
 
   Widget build() {
@@ -45,7 +33,7 @@ class Material extends Component {
       decoration: new BoxDecoration(
         boxShadow: shadows[level],
         borderRadius: edges[edge],
-        backgroundColor: backgroundColor,
+        backgroundColor: color,
         shape: edge == MaterialEdge.circle ? Shape.circle : Shape.rectangle
       ),
       child: new DefaultTextStyle(style: Theme.of(this).text.body1, child: child)