[runtime] Replace %to_string_fun with %_ToString.

src/runtime/runtime-date.cc

Index: src/runtime/runtime-date.cc
diff --git a/src/runtime/runtime-date.cc b/src/runtime/runtime-date.cc
index 4d238b443e2ed0a0e7582891a1721006bdf763d1..b4ed6bd33f4439806e437d08fe834426ddf246f6 100644
--- a/src/runtime/runtime-date.cc
+++ b/src/runtime/runtime-date.cc
@@ -100,8 +100,8 @@ RUNTIME_FUNCTION(Runtime_DateCurrentTime) {
 
 RUNTIME_FUNCTION(Runtime_DateParseString) {
   HandleScope scope(isolate);
-  DCHECK(args.length() == 2);
-  CONVERT_ARG_HANDLE_CHECKED(String, str, 0);
+  DCHECK_EQ(2, args.length());
+  CONVERT_ARG_HANDLE_CHECKED(Object, input, 0);
   CONVERT_ARG_HANDLE_CHECKED(JSArray, output, 1);
 
   RUNTIME_ASSERT(output->HasFastElements());
@@ -110,6 +110,10 @@ RUNTIME_FUNCTION(Runtime_DateParseString) {
   Handle<FixedArray> output_array(FixedArray::cast(output->elements()));
   RUNTIME_ASSERT(output_array->length() >= DateParser::OUTPUT_SIZE);
 
+  Handle<String> str;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, str,
+                                     Object::ToString(isolate, input));
+
   str = String::Flatten(str);
   DisallowHeapAllocation no_gc;