When using SDK outline, transplant its names into the name root.

pkg/kernel/lib/canonical_name.dart

Index: pkg/kernel/lib/canonical_name.dart
diff --git a/pkg/kernel/lib/canonical_name.dart b/pkg/kernel/lib/canonical_name.dart
index a56c482c23264d8f147c4f5d1f8c2d08833843f3..375453e4c423cb5ac0f42cfb492bf068187d8900 100644
--- a/pkg/kernel/lib/canonical_name.dart
+++ b/pkg/kernel/lib/canonical_name.dart
@@ -57,7 +57,7 @@ import 'ast.dart';
 /// The "qualified name" allows a member to have a name that is private to
 /// a library other than the one containing that member.
 class CanonicalName {
-  final CanonicalName parent;
+  CanonicalName _parent;
   final String name;
 
   Map<String, CanonicalName> _children;
@@ -68,16 +68,16 @@ class CanonicalName {
   /// Temporary index used during serialization.
   int index = -1;
 
-  CanonicalName._(this.parent, this.name) {
+  CanonicalName._(this._parent, this.name) {
     assert(name != null);
   }
 
-  CanonicalName.root()
-      : parent = null,
-        name = '';
+  CanonicalName.root() : name = '';
 
   bool get isRoot => parent == null;
 
+  CanonicalName get parent => _parent;
+
   Iterable<CanonicalName> get children =>
       _children?.values ?? const <CanonicalName>[];
 
@@ -112,6 +112,13 @@ class CanonicalName {
     _children?.remove(name);
   }
 
+  /// Transplant the given [child] into this name.
+  void transplantChild(CanonicalName child) {
+    var map = _children ??= <String, CanonicalName>{};
+    map[child.name] = child;
+    child._parent = this;
+  }
+
   void bindTo(Reference target) {
     if (reference == target) return;
     if (reference != null) {