Check for a passed-in type argument vector in the prolog of generic functions.

runtime/lib/internal_patch.dart

Index: runtime/lib/internal_patch.dart
diff --git a/runtime/lib/internal_patch.dart b/runtime/lib/internal_patch.dart
index cddf30ad4262172b81561cfa97effbde80317766..a5d9b2da2780983e51657db26cec765ddeac0081 100644
--- a/runtime/lib/internal_patch.dart
+++ b/runtime/lib/internal_patch.dart
@@ -64,3 +64,9 @@ class Lists {
     }
   }
 }
+
+// Prepend the parent type arguments (maybe null) to the function type
+// arguments (may be null). The result is null if both input vectors are null
+// or is a newly allocated and canonicalized vector of length 'len'.
+_prependTypeArguments(functionTypeArguments, parentTypeArguments, len)
+    native "Internal_prependTypeArguments";