[JSON] implement indentation in the BasicJsonStringifier and expose via API.

src/runtime/runtime.h

Index: src/runtime/runtime.h
diff --git a/src/runtime/runtime.h b/src/runtime/runtime.h
index 1873020c2397c7f5d0de0179cd8862d3be545933..749042abb30ba047beb84188338358e6f1c2adfe 100644
--- a/src/runtime/runtime.h
+++ b/src/runtime/runtime.h
@@ -324,10 +324,9 @@ namespace internal {
 
 #define FOR_EACH_INTRINSIC_JSON(F) \
   F(QuoteJSONString, 1, 1)         \
-  F(BasicJSONStringify, 1, 1)      \
+  F(BasicJSONStringify, 2, 1)      \
   F(ParseJson, 1, 1)
 
-
 #define FOR_EACH_INTRINSIC_LITERALS(F) \
   F(CreateRegExpLiteral, 4, 1)         \
   F(CreateObjectLiteral, 4, 1)         \
@@ -1094,7 +1093,7 @@ class Runtime : public AllStatic {
       Isolate* isolate, Handle<Object> object, Handle<Object> key);
 
   MUST_USE_RESULT static MaybeHandle<Object> BasicJsonStringify(
-      Isolate* isolate, Handle<Object> object);
+      Isolate* isolate, Handle<Object> object, Handle<String> gap);
 
   MUST_USE_RESULT static MaybeHandle<Object> BasicJsonStringifyString(
       Isolate* isolate, Handle<String> string);