Fix normalization of relative paths inside of deep relative imports

lib/build/import_crawler.dart

 // Copyright (c) 2013, 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 web_components.build.import_crawler;
 
 import 'dart:async';
 import 'dart:collection' show LinkedHashMap;
 import 'package:code_transformers/assets.dart';
 import 'package:code_transformers/messages/build_logger.dart';
 import 'package:barback/barback.dart';
 import 'package:html5lib/dom.dart' show Document, Element;
 import 'common.dart';
 import 'messages.dart';
 
 /// Information about an html import found in a document.
 class ImportData {
+  /// The [AssetId] where the html import appeared.
+  final AssetId fromId;
+
   /// The [Document] where the html import appeared.
   final Document document;
 
   /// The html import element itself.
   final Element element;
 
-  ImportData(this.document, this.element);
+  ImportData(this.document, this.element, {this.fromId});
 }
 
 /// A crawler for html imports.
 class ImportCrawler {
   // Can be either an AggregateTransform or Transform.
   final _transform;
   final BuildLogger _logger;
   final AssetId _primaryInputId;
 
   // Optional parsed document for the primary id if available.
   final Document _primaryDocument;
 
   ImportCrawler(this._transform, this._primaryInputId, this._logger,
       {Document primaryDocument})
       : _primaryDocument = primaryDocument;
 
   /// Returns a post-ordered map of [AssetId]'s to [ImportData]. The [AssetId]'s
   /// represent an asset which was discovered via an html import, and the
   /// [ImportData] represents the [Document] where it was discovered and the
   /// html import [Element] itself.
   Future<LinkedHashMap<AssetId, ImportData>> crawlImports() {
     var documents = new LinkedHashMap<AssetId, ImportData>();
     var seen = new Set<AssetId>();
 
-    Future doCrawl(AssetId assetId, [Element import, Document document]) {
+    Future doCrawl(AssetId assetId,
+        {Element import, Document document, AssetId from}) {
       if (seen.contains(assetId)) return null;
       seen.add(assetId);
 
       Future crawlImports(Document document) {
         var imports = document.querySelectorAll('link[rel="import"]');
-        var done =
-            Future.forEach(imports, (i) => doCrawl(_importId(assetId, i), i));
+        var done = Future.forEach(imports,
+            (i) => doCrawl(_importId(assetId, i), import: i, from: assetId));
 
         // Add this document after its dependencies.
         return done.then((_) {
-          documents[assetId] = new ImportData(document, import);
+          documents[assetId] = new ImportData(document, import, fromId: from);
         });
       }
 
       if (document != null) {
         return crawlImports(document);
       } else {
         return _transform.readInputAsString(assetId).then((html) {
           return crawlImports(parseHtml(html, assetId.path));
         }).catchError((error) {
           var span;
           if (import != null) span = import.sourceSpan;
           _logger.error(inlineImportFail.create({'error': error}), span: span);
         });
       }
     }
 
-    return
-      doCrawl(_primaryInputId, null, _primaryDocument).then((_) => documents);
+    return doCrawl(_primaryInputId, document: _primaryDocument)
+        .then((_) => documents);
   }
 
   AssetId _importId(AssetId source, Element import) {
     var url = import.attributes['href'];
     return uriToAssetId(source, url, _transform.logger, import.sourceSpan);
   }
 }