Make ElementLocationImpl.hashCode SMI, improve performance.

pkg/analyzer/lib/src/dart/element/element.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.dart.element.element;
 
 import 'dart:collection';
 import 'dart:math' show min;
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 2232 matching lines @@
       if (i > 0) {
         buffer.writeCharCode(_SEPARATOR_CHAR);
       }
       _encode(buffer, _components[i]);
     }
     return buffer.toString();
   }
 
   @override
   int get hashCode {
-    int result = 1;
+    int result = 0;
     for (int i = 0; i < _components.length; i++) {
       String component = _components[i];
-      result = 31 * result + component.hashCode;
+      result = JenkinsSmiHash.combine(result, component.hashCode);
     }
     return result;
   }
 
   @override
   bool operator ==(Object object) {
     if (identical(this, object)) {
       return true;
     }
     if (object is! ElementLocationImpl) {
@@ skipping 2664 matching lines @@
 
   @override
   void visitElement(Element element) {
     int offset = element.nameOffset;
     if (offset != -1) {
       map[offset] = element;
     }
     super.visitElement(element);
   }
 }