Split scannerlib.dart into several libraries.

pkg/compiler/lib/src/scanner/utf8_bytes_scanner.dart

Index: pkg/compiler/lib/src/scanner/utf8_bytes_scanner.dart
diff --git a/pkg/compiler/lib/src/scanner/utf8_bytes_scanner.dart b/pkg/compiler/lib/src/scanner/utf8_bytes_scanner.dart
index d919596154580c9a6e09b6a710dfafb7142d9544..13ab19e85cfa134f859f91fd6a4dcd06a4d231bd 100644
--- a/pkg/compiler/lib/src/scanner/utf8_bytes_scanner.dart
+++ b/pkg/compiler/lib/src/scanner/utf8_bytes_scanner.dart
@@ -2,7 +2,21 @@
 // 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