Add a way to use shared CanonicalName root to deserialize Program.

pkg/kernel/lib/ast.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// -----------------------------------------------------------------------
 ///                           ERROR HANDLING
 /// -----------------------------------------------------------------------
 ///
 /// As a rule of thumb, errors that can be detected statically are handled by
 /// the frontend, typically by translating the erroneous code into a 'throw' or
@@ skipping 4219 matching lines @@
     return hash;
   }
 }
 
 // ------------------------------------------------------------------------
 //                                PROGRAM
 // ------------------------------------------------------------------------
 
 /// A way to bundle up all the libraries in a program.
 class Program extends TreeNode {
-  final CanonicalName root = new CanonicalName.root();
+  final CanonicalName root;
 
   final List<Library> libraries;
 
   /// Map from a source file uri to a line-starts table and source code.
   /// Given a source file uri and a offset in that file one can translate
   /// it to a line:column position in that file.
   final Map<String, Source> uriToSource;
 
   /// Reference to the main method in one of the libraries.
   Reference mainMethodName;
 
-  Program([List<Library> libraries, Map<String, Source> uriToSource])
-      : libraries = libraries ?? <Library>[],
+  Program(
+      {CanonicalName nameRoot,
+      List<Library> libraries,
+      Map<String, Source> uriToSource})
+      : root = nameRoot ?? new CanonicalName.root(),
+        libraries = libraries ?? <Library>[],
         uriToSource = uriToSource ?? <String, Source>{} {
     setParents(this.libraries, this);
   }
 
   void computeCanonicalNames() {
     for (var library in libraries) {
       root.getChildFromUri(library.importUri).bindTo(library.reference);
       library.computeCanonicalNames();
     }
   }
@@ skipping 237 matching lines @@
 /// typedef has not been assigned a canonical name yet.
 ///
 /// Returns `null` if the typedef is `null`.
 CanonicalName getCanonicalNameOfTypedef(Typedef typedef_) {
   if (typedef_ == null) return null;
   if (typedef_.canonicalName == null) {
     throw '$typedef_ has no canonical name';
   }
   return typedef_.canonicalName;
 }