Merge kernel closure conversion into the Dart SDK

pkg/kernel/lib/import_table.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.import_table;
 
 import 'ast.dart';
 import 'package:path/path.dart' as path;
 
 abstract class ImportTable {
   int getImportIndex(Library library);
@@ skipping 70 matching lines @@
     if (targetUri == null) {
       throw '$referenceUri cannot refer to library without an import URI';
     }
     if (targetUri.scheme == 'file' && referenceUri.scheme == 'file') {
       var targetDirectory = path.dirname(targetUri.path);
       var currentDirectory = path.dirname(referenceUri.path);
       var relativeDirectory =
           path.relative(targetDirectory, from: currentDirectory);
       var filename = path.basename(targetUri.path);
       table.addImport(target, '$relativeDirectory/$filename');
-    } else if (targetUri.scheme == 'file') {
+    } else if (targetUri.scheme == 'file' && referenceUri.path != "_builtin") {

[asgerf, 2016/12/09 10:57:58]

Please add a comment explaining what this is

[karlklose, 2016/12/15 07:54:19]

Removed.

       // Cannot import a file:URI from a dart:URI or package:URI.
       // We may want to remove this restriction, but for now it's just a sanity
       // check.
       throw '$referenceUri cannot refer to application library $targetUri';
     } else {
       table.addImport(target, target.importUri.toString());
     }
   }
 
   visitClassReference(Class node) {
     addLibraryImport(node.enclosingLibrary);
   }
 
   defaultMemberReference(Member node) {
     addLibraryImport(node.enclosingLibrary);
   }
 
   visitName(Name name) {
     if (name.library != null) {
       addLibraryImport(name.library);
     }
   }
 }