Fraction class prototype and test (not to be committed).

runtime/vm/token.h

Index: runtime/vm/token.h
diff --git a/runtime/vm/token.h b/runtime/vm/token.h
index 6ddf17ba87b18a1288ca2303a222fcc49e5f51ad..be613524c7e268e8d5aed04efb17aea4f6bc3707 100644
--- a/runtime/vm/token.h
+++ b/runtime/vm/token.h
@@ -121,6 +121,7 @@ namespace dart {
   TOK(kIDENT, "", 0, kNoAttribute)                                             \
   TOK(kSTRING, "", 0, kNoAttribute)                                            \
   TOK(kINTEGER, "", 0, kNoAttribute)                                           \
+  TOK(kRATIONAL, "", 0, kNoAttribute)                                          \
   TOK(kDOUBLE, "", 0, kNoAttribute)                                            \
                                                                                \
   TOK(kINTERPOL_VAR, "$", 0, kNoAttribute)                                     \
@@ -292,6 +293,7 @@ class Token {
             (tok == Token::kSTRING) ||
             (tok == Token::kINTERPOL_VAR) ||
             (tok == Token::kERROR) ||
+            (tok == Token::kRATIONAL) ||
             (tok == Token::kDOUBLE));
   }