[WIP] NumberToString operator in TF.

src/runtime/runtime-numbers.cc

Index: src/runtime/runtime-numbers.cc
diff --git a/src/runtime/runtime-numbers.cc b/src/runtime/runtime-numbers.cc
index 9f43c0acfceeeff5bfec4d3fca72ebbf41830f2d..1c8c91d126a6356f56335fd9b6301100b635ae09 100644
--- a/src/runtime/runtime-numbers.cc
+++ b/src/runtime/runtime-numbers.cc
@@ -74,10 +74,21 @@ RUNTIME_FUNCTION(Runtime_StringParseFloat) {
 
 RUNTIME_FUNCTION(Runtime_NumberToString) {
   HandleScope scope(isolate);
-  DCHECK(args.length() == 1);
-  CONVERT_NUMBER_ARG_HANDLE_CHECKED(number, 0);
-
-  return *isolate->factory()->NumberToString(number);
+  DCHECK_LE(1, args.length());
+  DCHECK_GE(2, args.length());
+  CONVERT_NUMBER_ARG_HANDLE_CHECKED(value, 0);
+  if (args.length() == 1) return *isolate->factory()->NumberToString(value);
+  double value_number = value->Number();
+  CONVERT_INT32_ARG_CHECKED(radix, 1);
+  if (std::isnan(value_number)) return isolate->heap()->nan_string();
+  if (std::isinf(value_number)) {
+    return (value_number < 0.0) ? isolate->heap()->minus_infinity_string()
+                                : isolate->heap()->infinity_string();
+  }
+  char* const str = DoubleToRadixCString(value_number, radix);
+  Handle<String> result = isolate->factory()->NewStringFromAsciiChecked(str);
+  DeleteArray(str);
+  return *result;
 }