Fix for extracting from interpolated string.

pkg/analysis_server/lib/src/services/refactoring/extract_local.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 services.src.refactoring.extract_local;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analysis_server/src/protocol_server.dart' hide Element;
@@ skipping 531 matching lines @@
 
   @override
   Object visitExpression(Expression node) {
     if (ref._isExtractable(rangeNode(node))) {
       _tryToFindOccurrence(node);
     }
     return super.visitExpression(node);
   }
 
   @override
-  Object visitSimpleStringLiteral(SimpleStringLiteral node) {
+  Object visitStringLiteral(StringLiteral node) {
     if (ref.stringLiteralPart != null) {
       int occuLength = ref.stringLiteralPart.length;
-      String value = node.value;
-      int valueOffset = node.offset + (node.isMultiline ? 3 : 1);
+      String value = ref.utils.getNodeText(node);
       int lastIndex = 0;
       while (true) {
         int index = value.indexOf(ref.stringLiteralPart, lastIndex);
         if (index == -1) {
           break;
         }
         lastIndex = index + occuLength;
-        int occuStart = valueOffset + index;
+        int occuStart = node.offset + index;
         SourceRange occuRange = rangeStartLength(occuStart, occuLength);
         occurrences.add(occuRange);
       }
       return null;
     }
     return visitExpression(node);
   }
 
   void _addOccurrence(SourceRange range) {
     if (range.intersects(ref.selectionRange)) {
@@ skipping 55 matching lines @@
 
   _TokenLocalElementVisitor(this.map);
 
   visitSimpleIdentifier(SimpleIdentifier node) {
     Element element = node.staticElement;
     if (element is LocalVariableElement) {
       map[node.token] = element;
     }
   }
 }