Tab bar should have white indicator if primary and accent color are the same

sky/sdk/lib/widgets/tabs.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 'dart:math' as math;
 
 import 'package:sky/animation/generators.dart';
 import 'package:sky/animation/mechanics.dart';
 import 'package:sky/animation/scroll_behavior.dart';
 import 'package:sky/painting/text_style.dart';
 import 'package:sky/rendering/box.dart';
 import 'package:sky/rendering/object.dart';
 import 'package:vector_math/vector_math.dart';
+import 'package:sky/theme/colors.dart' as colors;
 import 'package:sky/widgets/basic.dart';
 import 'package:sky/widgets/icon.dart';
 import 'package:sky/widgets/ink_well.dart';
 import 'package:sky/widgets/scrollable.dart';
 import 'package:sky/widgets/theme.dart';
 import 'package:sky/widgets/widget.dart';
 
 typedef void SelectedIndexChanged(int selectedIndex);
 typedef void LayoutChanged(Size size, List<double> widths);
 
@@ skipping 402 matching lines @@
     assert(labels != null && labels.isNotEmpty);
     List<Widget> tabs = <Widget>[];
     bool textAndIcons = false;
     int tabIndex = 0;
     for (TabLabel label in labels) {
       tabs.add(_toTab(label, tabIndex++));
       if (label.text != null && label.icon != null)
         textAndIcons = true;
     }
 
+    Color backgroundColor = Theme.of(this).primaryColor;
+    Color indicatorColor = Theme.of(this).accentColor;
+    if (indicatorColor == backgroundColor) {
+      indicatorColor = colors.White;
+    }
+
     TabBarWrapper tabBarWrapper = new TabBarWrapper(
       children: tabs, 
       selectedIndex: selectedIndex,
-      backgroundColor: Theme.of(this).primaryColor,
-      indicatorColor: Theme.of(this).accentColor,
+      backgroundColor: backgroundColor,
+      indicatorColor: indicatorColor,
       textAndIcons: textAndIcons,
       scrollable: scrollable,
       onLayoutChanged: scrollable ? _layoutChanged : null
     );
 
     Matrix4 transform = new Matrix4.identity();
     transform.translate(-scrollOffset, 0.0);
     return new Transform(child: tabBarWrapper, transform: transform);
   }
 }
@@ skipping 41 matching lines @@
       selectedIndex: selectedIndex,
       scrollable: scrollable
     );
 
     Widget content = views[selectedIndex].buildContent();
     return new Flex([tabBar, new Flexible(child: content)],
       direction: FlexDirection.vertical
     );
   }
 }