[torque] Fix Signature printing

The operator<< for Signature objects in Torque incorrectly counted
the number of named parameters instead of the total number
of parameters when displaying them.

This would cause the displayed signature to be "()" when no
parameters were named, instead of the actual signature.

Change-Id: I32572da5f5a378b71749515d89429172129bbcb9
Reviewed-on: https://chromium-review.googlesource.com/1104172Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Théotime Grohens <theotime@google.com>
Cr-Commit-Position: refs/heads/master@{#53792}

src/torque/types.cc

@@ -150,7 +150,7 @@ std::string UnionType::GetGeneratedTNodeTypeName() const {
 
 std::ostream& operator<<(std::ostream& os, const Signature& sig) {
   os << "(";
-  for (size_t i = 0; i < sig.parameter_names.size(); ++i) {
+  for (size_t i = 0; i < sig.parameter_types.types.size(); ++i) {
     if (i > 0) os << ", ";
     if (!sig.parameter_names.empty()) os << sig.parameter_names[i] << ": ";
     os << sig.parameter_types.types[i];