switch html5lib to new pkg layout

lib/src/inputstream.dart

 #library('inputstream');
 
 #import('dart:io');
 #import('dart:utf');
 #import('char_encodings.dart');
 #import('constants.dart');
 #import('utils.dart');
 #import('encoding_parser.dart');
-#import('../treebuilders/simpletree.dart', prefix: 'tree'); // for Span
+#import('../dom.dart', prefix: 'dom'); // for Span
 
 /**
  * Provides a unicode stream of characters to the HTMLTokenizer.
  *
  * This class takes care of character encoding and removing or replacing
  * incorrect byte-sequences and also provides column and line tracking.
  */
 class HTMLInputStream {
 
   const int _defaultChunkSize = 10240;
@@ skipping 165 matching lines @@
     var parser = new EncodingParser(slice(rawBytes, 0, numBytesMeta));
     var encoding = parser.getEncoding();
 
     if (const ["utf-16", "utf-16-be", "utf-16-le"].indexOf(encoding) >= 0) {
       encoding = "utf-8";
     }
 
     return encoding;
   }
 
-  tree.Span _position(int offset) {
+  dom.Span _position(int offset) {
     var nLines = 1;
     var lastLinePos = -1;
     for (int i = 0; i < offset; i++) {
       if (chunk.charCodeAt(i) == NEWLINE) {
         lastLinePos = i;
         nLines++;
       }
     }
     var positionLine = prevNumLines + nLines;
     var positionColumn;
     if (lastLinePos == -1) {
       positionColumn = prevNumCols + offset;
     } else {
       positionColumn = offset - (lastLinePos + 1);
     }
-    return new tree.Span(positionLine, positionColumn);
+    return new dom.Span(positionLine, positionColumn);
   }
 
   /** Returns (line, col) of the current position in the stream. */
-  tree.Span position() => _position(chunkOffset);
+  dom.Span position() => _position(chunkOffset);
 
   /**
    * Read one character from the stream or queue if available. Return
    * EOF when EOF is reached.
    */
   String char() {
     // Read a new chunk from the input stream if necessary
     if (chunkOffset >= chunk.length) {
       if (!readChunk()) {
         return EOF;
@@ skipping 198 matching lines @@
  * string doesn't correspond to a valid encoding.
  */
 String codecName(String encoding) {
   final asciiPunctuation = const RegExp(
       "[\u0009-\u000D\u0020-\u002F\u003A-\u0040\u005B-\u0060\u007B-\u007E]");
 
   if (encoding == null) return null;
   var canonicalName = encoding.replaceAll(asciiPunctuation, '').toLowerCase();
   return encodings[canonicalName];
 }