Fix the build by removing a not-yet needed method

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 engine.source;
 
 import 'dart:collection';
 import "dart:math" as math;
 
 import 'package:analyzer/file_system/file_system.dart';
@@ skipping 190 matching lines @@
    * @param lineStarts the offsets of the first character of each line in the source code
    */
   LineInfo(this._lineStarts) {
     if (_lineStarts == null) {
       throw new IllegalArgumentException("lineStarts must be non-null");
     } else if (_lineStarts.length < 1) {
       throw new IllegalArgumentException("lineStarts must be non-empty");
     }
   }
 
-  /**
-   * Return the offset of the first character on the line with the given
-   * [lineNumber].
-   */
-  int getLineOffset(int lineNumber) {
-    if (lineNumber < 0 || lineNumber >= _lineStarts.length) {
-      throw new ArgumentError('Invalid line number: $lineNumber');
-    }
-    return _lineStarts[lineNumber];
-  }
+//  /**
+//   * Return the offset of the first character on the line with the given
+//   * [lineNumber].
+//   */
+//  int getLineOffset(int lineNumber) {
+//    if (lineNumber < 0 || lineNumber >= _lineStarts.length) {
+//      throw new ArgumentError('Invalid line number: $lineNumber');
+//    }
+//    return _lineStarts[lineNumber];
+//  }
 
   /**
    * Return the location information for the character at the given offset.
    *
    * @param offset the offset of the character for which location information is to be returned
    * @return the location information for the character at the given offset
    */
   LineInfo_Location getLocation(int offset) {
     var min = 0;
     var max = _lineStarts.length - 1;
@@ skipping 857 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;
 }