Let's hide double.INFINITY a bit more, by providing cleaner APIs for the cases where we're currentl…

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 'dart:sky' as sky;
 
 import 'package:sky/painting/text_style.dart';
 import 'package:sky/rendering/box.dart';
 import 'package:sky/rendering/object.dart';
@@ skipping 76 matching lines @@
       assert(child.parentData is TabBarParentData);
       child = child.parentData.nextSibling;
     }
     return childCount;
   }
 
   void performLayout() {
     assert(constraints is BoxConstraints);
 
     size = constraints.constrain(new Size(constraints.maxWidth, _kTabBarHeight));
-    assert(size.width < double.INFINITY);
-    assert(size.height < double.INFINITY);
+    assert(!size.isInfinite);
 
     int childCount = _childCount();
     if (childCount == 0)
       return;
 
     double tabWidth = size.width / childCount;
     BoxConstraints tabConstraints =
       new BoxConstraints.tightFor(width: tabWidth, height: size.height);
     double x = 0.0;
     RenderBox child = firstChild;
@@ skipping 144 matching lines @@
     assert(labels != null && labels.isNotEmpty);
     List<Widget> tabs = <Widget>[];
     for (int tabIndex = 0; tabIndex < labels.length; tabIndex++) {
       tabs.add(_toTab(labels[tabIndex], tabIndex));
     }
     return new TabBarWrapper(tabs, selectedIndex);
   }
 }