Stub implementation of patch invariants for the patch refactoring.

lib/compiler/implementation/scanner/token.dart

Index: lib/compiler/implementation/scanner/token.dart
diff --git a/lib/compiler/implementation/scanner/token.dart b/lib/compiler/implementation/scanner/token.dart
index 7646e4ef6cec1bf630b10de77e386f68acedd7a4..75e35770de428ccd3019596998e55ad191764a86 100644
--- a/lib/compiler/implementation/scanner/token.dart
+++ b/lib/compiler/implementation/scanner/token.dart
@@ -84,7 +84,7 @@ const int UNKNOWN_TOKEN = 1024;
 /**
  * A token that doubles as a linked list.
  */
-class Token {
+class Token implements Spanable {
   /**
    * The precedence info for this token. [info] determines the kind and the
    * precedence level of this token.