Include dart/test_all into src/test_all and fix element tests.

pkg/analyzer/lib/src/generated/source.dart

 // Copyright (c) 2014, 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 analyzer.src.generated.source;
 
 import 'dart:collection';
 import "dart:math" as math;
 
 import 'package:analyzer/file_system/file_system.dart';
@@ skipping 361 matching lines @@
   final UriKind uriKind;
 
   NonExistingSource(this.fullName, this.uri, this.uriKind);
 
   @override
   TimestampedData<String> get contents {
     throw new UnsupportedOperationException('$fullName does not exist.');
   }
 
   @override
-  String get encoding {
-    throw new UnsupportedOperationException('$fullName does not exist.');
-  }
+  String get encoding => uri.toString();
 
   @override
   int get hashCode => fullName.hashCode;
 
   @override
   bool get isInSystemLibrary => false;
 
   @override
   int get modificationStamp => -1;
 
@@ skipping 538 matching lines @@
   Source resolveAbsolute(Uri uri, [Uri actualUri]);
 
   /**
    * Return an absolute URI that represents the given [source], or `null` if a
    * valid URI cannot be computed.
    *
    * The computation should be based solely on [source.fullName].
    */
   Uri restoreAbsolute(Source source) => null;
 }