Split scannerlib.dart into several libraries.

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

Index: pkg/compiler/lib/src/scanner/string_scanner.dart
diff --git a/pkg/compiler/lib/src/scanner/string_scanner.dart b/pkg/compiler/lib/src/scanner/string_scanner.dart
index 5a30e433cb4feed7fc3755da998ae1ddaa88a1be..47c6711d4b2812f001e017c922b9b92483ca1507 100644
--- a/pkg/compiler/lib/src/scanner/string_scanner.dart
+++ b/pkg/compiler/lib/src/scanner/string_scanner.dart
@@ -2,7 +2,18 @@
 // 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.string;
+
+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 String and creates tokens that points to