Implement cascaded calls.

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 215ec18d058b269036e0a0bb9228e3c05fa9b3e8..f94c998f8a312c09f41cd4b392b0eb7e0d17288d 100644
--- a/lib/compiler/implementation/scanner/token.dart
+++ b/lib/compiler/implementation/scanner/token.dart
@@ -248,9 +248,13 @@ final PrecedenceInfo PERIOD_PERIOD_PERIOD_INFO =
   const PrecedenceInfo(const SourceString('...'), 0,
                        PERIOD_PERIOD_PERIOD_TOKEN);
 
-// TODO(ahe): This might become a token.
+/**
+ * The cascade operator has the lowest precedence of any operator.
+ */
+final int CASCADE_PRECEDENCE = 1;
 final PrecedenceInfo PERIOD_PERIOD_INFO =
-  const PrecedenceInfo(const SourceString('..'), 0, PERIOD_PERIOD_TOKEN);
+  const PrecedenceInfo(const SourceString('..'), CASCADE_PRECEDENCE,
+                       PERIOD_PERIOD_TOKEN);
 
 final PrecedenceInfo BANG_INFO =
   const PrecedenceInfo(const SourceString('!'), 0, BANG_TOKEN);
@@ -436,4 +440,4 @@ final PrecedenceInfo HEXADECIMAL_INFO =
 
 // For reporting lexical errors.
 final PrecedenceInfo ERROR_INFO =
-  const PrecedenceInfo(const SourceString('?'), 0, UNKNOWN_TOKEN);
+  const PrecedenceInfo(const SourceString('?'), 0, UNKNOWN_TOKEN);