Move RenderTogglable to material.dart

Fixes #219

packages/flutter/lib/material.dart

@@ -54,6 +54,7 @@ export 'src/material/theme_data.dart';
 export 'src/material/time_picker.dart';
 export 'src/material/time_picker_dialog.dart';
 export 'src/material/title.dart';
+export 'src/material/toggleable.dart';
 export 'src/material/tool_bar.dart';
 export 'src/material/typography.dart';
 

packages/flutter/lib/rendering.dart

@@ -27,7 +27,6 @@ export 'src/rendering/proxy_box.dart';
 export 'src/rendering/shifted_box.dart';
 export 'src/rendering/stack.dart';
 export 'src/rendering/statistics_box.dart';
-export 'src/rendering/toggleable.dart';
 export 'src/rendering/view.dart';
 export 'src/rendering/viewport.dart';
 

packages/flutter/lib/src/material/checkbox.dart

@@ -9,6 +9,7 @@ import 'package:flutter/widgets.dart';
 
 import 'colors.dart';
 import 'theme.dart';
+import 'toggleable.dart';
 
 const double _kMidpoint = 0.5;
 const double _kEdgeSize = 18.0;

packages/flutter/lib/src/material/switch.dart

@@ -12,6 +12,7 @@ import 'package:flutter/widgets.dart';
 import 'radial_reaction.dart';
 import 'shadows.dart';
 import 'theme.dart';
+import 'toggleable.dart';
 
 const Color _kThumbOffColor = const Color(0xFFFAFAFA);
 const Color _kTrackOffColor = const Color(0x42000000);

packages/flutter/lib/src/material/toggleable.dart

@@ -4,13 +4,7 @@
 
 import 'package:flutter/animation.dart';
 import 'package:flutter/gestures.dart';
-
+import 'package:flutter/rendering.dart';
-import 'binding.dart';
-import 'box.dart';
-import 'object.dart';
-import 'proxy_box.dart';
-
-typedef void ValueChanged<T>(T value);
 
 const Duration _kToggleDuration = const Duration(milliseconds: 200);
 

packages/flutter/lib/src/rendering/basic_types.dart

@@ -14,3 +14,5 @@ export 'dart:ui' show
   Size,
   TransferMode,
   VoidCallback;
+
+typedef void ValueChanged<T>(T value);