Remove circular imports of the material.dart library

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

@@ -6,13 +6,14 @@ import 'dart:async';
 
 import 'package:intl/date_symbols.dart';
 import 'package:intl/intl.dart';
-import 'package:sky/material.dart';
 import 'package:sky/painting.dart';
 import 'package:sky/services.dart';
 import 'package:sky/widgets.dart';
 
+import 'colors.dart';
 import 'ink_well.dart';
 import 'theme.dart';
+import 'typography.dart';
 
 typedef void DatePickerValueChanged(DateTime dateTime);
 

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

@@ -6,11 +6,11 @@ import 'dart:async';
 
 import 'package:sky/animation.dart';
 import 'package:sky/gestures.dart';
-import 'package:sky/material.dart';
 import 'package:sky/widgets.dart';
 
-import 'material.dart';
+import 'colors.dart';
 import 'material_button.dart';
+import 'material.dart';
 import 'theme.dart';
 
 typedef Widget DialogBuilder(NavigatorState navigator);

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

@@ -3,9 +3,10 @@
 // found in the LICENSE file.
 
 import 'package:sky/animation.dart';
-import 'package:sky/material.dart';
 import 'package:sky/widgets.dart';
 
+import 'colors.dart';
+import 'shadows.dart';
 import 'theme.dart';
 
 // TODO(eseidel): Draw width should vary based on device size:

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

@@ -2,9 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'package:sky/material.dart';
 import 'package:sky/widgets.dart';
 
+import 'constants.dart';
 import 'theme.dart';
 
 // TODO(jackson): This class should usually render the user's

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

@@ -5,10 +5,10 @@
 import 'dart:sky' as sky;
 
 import 'package:sky/gestures.dart';
-import 'package:sky/material.dart';
 import 'package:sky/painting.dart';
 import 'package:sky/widgets.dart';
 
+import 'colors.dart';
 import 'icon.dart';
 import 'ink_well.dart';
 import 'theme.dart';

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

@@ -3,9 +3,9 @@
 // found in the LICENSE file.
 
 import 'package:sky/gestures.dart';
-import 'package:sky/material.dart';
 import 'package:sky/widgets.dart';
 
+import 'colors.dart';
 import 'material_button.dart';
 import 'theme.dart';
 

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

@@ -4,9 +4,10 @@
 
 import 'package:sky/animation.dart';
 import 'package:sky/painting.dart';
-import 'package:sky/material.dart';
 import 'package:sky/widgets.dart';
 
+import 'constants.dart';
+import 'shadows.dart';
 import 'theme.dart';
 
 enum MaterialType { canvas, card, circle, button }

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

@@ -4,7 +4,6 @@
 
 import 'dart:sky' as sky;
 
-import 'package:sky/material.dart';
 import 'package:sky/painting.dart';
 import 'package:sky/services.dart';
 import 'package:sky/widgets.dart';

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

@@ -3,9 +3,9 @@
 // found in the LICENSE file.
 
 import 'package:sky/gestures.dart';
-import 'package:sky/material.dart';
 import 'package:sky/widgets.dart';
 
+import 'colors.dart';
 import 'ink_well.dart';
 import 'material.dart';
 import 'theme.dart';

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

@@ -6,12 +6,12 @@ import 'dart:async';
 import 'dart:sky' as sky;
 
 import 'package:sky/animation.dart';
-import 'package:sky/material.dart';
 import 'package:sky/painting.dart';
 import 'package:sky/widgets.dart';
 
 import 'ink_well.dart';
 import 'popup_menu_item.dart';
+import 'shadows.dart';
 import 'theme.dart';
 
 const Duration _kMenuDuration = const Duration(milliseconds: 300);

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

@@ -3,9 +3,9 @@
 // found in the LICENSE file.
 
 import 'package:sky/gestures.dart';
-import 'package:sky/material.dart';
 import 'package:sky/widgets.dart';
 
+import 'colors.dart';
 import 'material_button.dart';
 import 'theme.dart';
 

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

@@ -4,10 +4,11 @@
 
 import 'dart:sky' as sky;
 
-import 'package:sky/material.dart';
 import 'package:sky/rendering.dart';
 import 'package:sky/widgets.dart';
 
+import 'constants.dart';
+
 class Scaffold extends StatelessComponent {
   Scaffold({
     Key key,

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

@@ -4,12 +4,13 @@
 
 import 'package:sky/animation.dart';
 import 'package:sky/gestures.dart';
-import 'package:sky/material.dart';
 import 'package:sky/painting.dart';
 import 'package:sky/widgets.dart';
 
+import 'constants.dart';
 import 'material.dart';
 import 'theme.dart';
+import 'typography.dart';
 
 const double _kSideMargins = 24.0;
 const double _kVerticalPadding = 14.0;

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

@@ -2,12 +2,14 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'package:sky/material.dart';
 import 'package:sky/painting.dart';
 import 'package:sky/widgets.dart';
 
+import 'constants.dart';
 import 'icon.dart';
+import 'shadows.dart';
 import 'theme.dart';
+import 'typography.dart';
 
 class ToolBar extends StatelessComponent {
   ToolBar({