Parse HTML files with keeping original attributes case.

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/generated/engine.dart';
@@ skipping 295 matching lines @@
         }
       }
 
       outputs[HTML_DOCUMENT] = new Document();
       outputs[HTML_DOCUMENT_ERRORS] = <AnalysisError>[
         new AnalysisError(
             target.source, 0, 0, ScannerErrorCode.UNABLE_GET_CONTENT, [message])
       ];
       outputs[LINE_INFO] = new LineInfo(<int>[0]);
     } else {
-      HtmlParser parser = new HtmlParser(content, generateSpans: true);
+      HtmlParser parser = new HtmlParser(content,
+          generateSpans: true, lowercaseAttrName: false);
       parser.compatMode = 'quirks';
       Document document = parser.parse();
       //
       // Convert errors.
       //
       List<AnalysisError> errors = <AnalysisError>[];
       // TODO(scheglov) https://github.com/dart-lang/sdk/issues/24643
 //      List<ParseError> parseErrors = parser.errors;
 //      for (ParseError parseError in parseErrors) {
 //        if (parseError.errorCode == 'expected-doctype-but-got-start-tag') {
@@ skipping 63 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);
 }