Consolidate duplicate code for resloving URIs.

pkg/analyzer/lib/src/task/html.dart

 // Copyright (c) 2015, 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.task.html;
 
 import 'dart:collection';
 
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/dart/scanner/scanner.dart';
@@ skipping 70 matching lines @@
 
   @override
   Uri get uri => throw new StateError('uri not supported for scripts');
 
   @override
   UriKind get uriKind =>
       throw new StateError('uriKind not supported for scripts');
 
   @override
   bool exists() => source.exists();
-
-  @override
-  Uri resolveRelativeUri(Uri relativeUri) =>
-      throw new StateError('resolveRelativeUri not supported for scripts');
 }
 
 /**
  * A task that looks for Dart scripts in an HTML file and computes both the Dart
  * libraries that are referenced by those scripts and the embedded Dart scripts.
  */
 class DartScriptsTask extends SourceBasedAnalysisTask {
   /**
    * The name of the [HTML_DOCUMENT] input.
    */
@@ skipping 301 matching lines @@
    * The content of the fragment.
    */
   final String content;
 
   /**
    * Initialize a newly created script fragment to have the given [offset] and
    * [content].
    */
   ScriptFragment(this.offset, this.line, this.column, this.content);
 }