Fixups

chrome-os-best-practices/lib/main.dart

@@ -181,7 +181,7 @@ class ChatScreenState extends State<ChatScreen> with TickerProviderStateMixin {
       child: Container(
         margin: const EdgeInsets.symmetric(horizontal: 8.0),
         child: Row(
-          children: <Widget>[
+          children: [
             Flexible(
               child: TextField(
                 controller: _textController,
@@ -248,7 +248,7 @@ class ChatMessage extends StatelessWidget {
         margin: const EdgeInsets.symmetric(vertical: 10.0),
         child: Row(
           crossAxisAlignment: CrossAxisAlignment.start,
-          children: <Widget>[
+          children: [
             Container(
               margin: const EdgeInsets.only(right: 16.0),
               child: CircleAvatar(child: Text(name[0])),

chrome-os-best-practices/pubspec.lock

@@ -7,7 +7,7 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.2.0"
+    version: "2.1.0"
   boolean_selector:
     dependency: transitive
     description:
@@ -80,7 +80,7 @@ packages:
       name: quiver
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.3"
+    version: "2.0.2"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -127,7 +127,7 @@ packages:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.5"
+    version: "0.2.4"
   typed_data:
     dependency: transitive
     description:
@@ -143,4 +143,4 @@ packages:
     source: hosted
     version: "2.0.8"
 sdks:
-  dart: ">=2.2.0 <3.0.0"
+  dart: ">=2.3.0-dev <3.0.0"

chrome-os-best-practices/pubspec.yaml

@@ -14,7 +14,7 @@ description: A new Flutter application.
 version: 1.0.0+1
 
 environment:
-  sdk: ">=2.1.0 <3.0.0"
+  sdk: ">=2.3.0-dev <3.0.0"
 
 dependencies:
   flutter:

chrome-os-best-practices/test/widget_test.dart

@@ -11,7 +11,7 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:friendlychat/main.dart';
 
 void main() {
-  testWidgets('Counter increments smoke test', (WidgetTester tester) async {
+  testWidgets('Counter increments smoke test', (tester) async {
     // Build our app and trigger a frame.
     await tester.pumpWidget(FriendlychatApp());
 

flutter_maps_firestore/pubspec.lock

@@ -7,7 +7,7 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.2.0"
+    version: "2.1.0"
   boolean_selector:
     dependency: transitive
     description:
@@ -122,7 +122,7 @@ packages:
       name: quiver
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.3"
+    version: "2.0.2"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -169,7 +169,7 @@ packages:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.5"
+    version: "0.2.4"
   typed_data:
     dependency: transitive
     description:

isolate_example/pubspec.lock

@@ -7,7 +7,7 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.2.0"
+    version: "2.1.0"
   boolean_selector:
     dependency: transitive
     description:
@@ -87,7 +87,7 @@ packages:
       name: quiver
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.3"
+    version: "2.0.2"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -134,7 +134,7 @@ packages:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.5"
+    version: "0.2.4"
   typed_data:
     dependency: transitive
     description:

jsonexample/pubspec.lock

@@ -28,7 +28,7 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.2.0"
+    version: "2.1.0"
   boolean_selector:
     dependency: transitive
     description:
@@ -332,7 +332,7 @@ packages:
       name: quiver
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.3"
+    version: "2.0.2"
   shelf:
     dependency: transitive
     description:
@@ -407,7 +407,7 @@ packages:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.5"
+    version: "0.2.4"
   timing:
     dependency: transitive
     description: