Sort the output (for now just the classes and instance members).

lib/compiler/implementation/scanner/string_scanner.dart

Index: lib/compiler/implementation/scanner/string_scanner.dart
diff --git a/lib/compiler/implementation/scanner/string_scanner.dart b/lib/compiler/implementation/scanner/string_scanner.dart
index 2f295abf39edb08f4315e72072c2f51e8a3519f4..d7f6167f7f08e5f6a6138f7ab40094249f8b90d1 100644
--- a/lib/compiler/implementation/scanner/string_scanner.dart
+++ b/lib/compiler/implementation/scanner/string_scanner.dart
@@ -42,6 +42,7 @@ class SubstringWrapper implements SourceString {
                          int this.begin, int this.end);
 
   int hashCode() => slowToString().hashCode();
+  int compareTo(SourceString other) => sourceStringCompare(this, other);
 
   bool operator ==(other) {
     return other is SourceString && slowToString() == other.slowToString();