Split scannerlib.dart into several libraries.

pkg/compiler/lib/src/scanner/utf8_bytes_scanner.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.
 
-part of scanner;
+library dart2js.scanner.utf8;
+
+import 'dart:convert' show
+    UNICODE_BOM_CHARACTER_RUNE,
+    UTF8;
+
+import '../io/source_file.dart' show
+    SourceFile;
+
+import 'array_based_scanner.dart' show
+    ArrayBasedScanner;
+import 'token.dart' show
+    PrecedenceInfo,
+    StringToken,
+    Token;
 
 /**
  * Scanner that reads from a UTF-8 encoded list of bytes and creates tokens
  * that points to substrings.
  */
 class Utf8BytesScanner extends ArrayBasedScanner {
   /**
    * The file content.
    *
    * The content is zero-terminated.
@@ skipping 182 matching lines @@
 
   void appendSubstringToken(PrecedenceInfo info, int start, bool asciiOnly,
                             [int extraOffset = 0]) {
     tail.next = new StringToken.fromUtf8Bytes(
         info, bytes, start, byteOffset + extraOffset, asciiOnly, tokenStart);
     tail = tail.next;
   }
 
   bool atEndOfFile() => byteOffset >= bytes.length - 1;
 }