Implement canonical name scheme in kernel.

pkg/kernel/lib/text/ast_to_text.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.
 library kernel.ast_to_text;
 
 import '../ast.dart';
 import '../import_table.dart';
 import '../type_propagation/type_propagation.dart';
 
 class Namer<T> {
@@ skipping 19 matching lines @@
         ++i;
       }
       return '$proposedName$i';
     });
   }
 }
 
 NameSystem globalDebuggingNames = new NameSystem();
 
 String debugLibraryName(Library node) {
-  return node.name ?? globalDebuggingNames.nameLibrary(node);
+  return node == null
+      ? 'null'
+      : node.name ?? globalDebuggingNames.nameLibrary(node);
 }
 
 String debugClassName(Class node) {
-  return node.name ?? globalDebuggingNames.nameClass(node);
+  return node == null
+      ? 'null'
+      : node.name ?? globalDebuggingNames.nameClass(node);
 }
 
 String debugQualifiedClassName(Class node) {
   return debugLibraryName(node.enclosingLibrary) + '::' + debugClassName(node);
 }
 
 String debugMemberName(Member node) {
   return node.name?.name ?? globalDebuggingNames.nameMember(node);
 }
 
@@ skipping 1498 matching lines @@
   }
   throw 'illegal ProcedureKind: $kind';
 }
 
 class ExpressionPrinter {
   final Printer writeer;
   final int minimumPrecedence;
 
   ExpressionPrinter(this.writeer, this.minimumPrecedence);
 }