Add support for ^ constraints in pub.

sdk/lib/_internal/pub_generated/lib/src/validator.dart

Index: sdk/lib/_internal/pub_generated/lib/src/validator.dart
diff --git a/sdk/lib/_internal/pub_generated/lib/src/validator.dart b/sdk/lib/_internal/pub_generated/lib/src/validator.dart
index 4580ca1325ac1439f1c328cb4ecf57b64ef968f8..25e68435d3ba396519f991cf62f01fe9e55bc848 100644
--- a/sdk/lib/_internal/pub_generated/lib/src/validator.dart
+++ b/sdk/lib/_internal/pub_generated/lib/src/validator.dart
@@ -17,6 +17,7 @@ import 'validator/executable.dart';
 import 'validator/license.dart';
 import 'validator/name.dart';
 import 'validator/pubspec_field.dart';
+import 'validator/sdk_constraint.dart';
 import 'validator/size.dart';
 import 'validator/utf8_readme.dart';
 
@@ -65,7 +66,8 @@ abstract class Validator {
         new DirectoryValidator(entrypoint),
         new ExecutableValidator(entrypoint),
         new CompiledDartdocValidator(entrypoint),
-        new Utf8ReadmeValidator(entrypoint)];
+        new Utf8ReadmeValidator(entrypoint),
+        new SdkConstraintValidator(entrypoint)];
     if (packageSize != null) {
       validators.add(new SizeValidator(entrypoint, packageSize));
     }