Install before starting the server if the lockfile is out of date.

sdk/lib/_internal/pub/lib/src/package.dart

Index: sdk/lib/_internal/pub/lib/src/package.dart
diff --git a/sdk/lib/_internal/pub/lib/src/package.dart b/sdk/lib/_internal/pub/lib/src/package.dart
index 6f1be0b4585c82dca6289c0eb7cf36c76504cb48..315f189a31648d52eb0c76b1fd605289e5fd8c4b 100644
--- a/sdk/lib/_internal/pub/lib/src/package.dart
+++ b/sdk/lib/_internal/pub/lib/src/package.dart
@@ -34,10 +34,12 @@ class Package {
   /// The parsed pubspec associated with this package.
   final Pubspec pubspec;
 
-  /// The ids of the packages that this package depends on. This is what is
-  /// specified in the pubspec when this package depends on another.
+  /// The immediate dependencies this package specifies in its pubspec.
   List<PackageDep> get dependencies => pubspec.dependencies;
 
+  /// The immediate dev dependencies this package specifies in its pubspec.
+  List<PackageDep> get devDependencies => pubspec.devDependencies;
+
   /// Returns the path to the README file at the root of the entrypoint, or null
   /// if no README file is found. If multiple READMEs are found, this uses the
   /// same conventions as pub.dartlang.org for choosing the primary one: the