[Merge chakra-core/ChakraCore@40d6222ef2] [MERGE #3861 @obastemur] js…

…rt: JsConvertValueToString exit fast if arg. is JavascriptString

Merge pull request #3861 from obastemur:wayward_giant

Entering into ContextAPIWrapper is expensive. node-chakracore, (epscially acme air app)
majority of the callers triggers this method with JavascriptString.

deps/chakrashim/core/lib/Jsrt/Jsrt.cpp

@@ -1215,12 +1215,22 @@ CHAKRA_API JsStringToPointer(_In_ JsValueRef stringValue, _Outptr_result_buffer_
 
 CHAKRA_API JsConvertValueToString(_In_ JsValueRef value, _Out_ JsValueRef *result)
 {
+    PARAM_NOT_NULL(result);
+    *result = nullptr;
+
+    if (value != nullptr && Js::JavascriptString::Is(value))
+    {
+        return ContextAPINoScriptWrapper_NoRecord([&](Js::ScriptContext *scriptContext) -> JsErrorCode {
+            VALIDATE_INCOMING_REFERENCE(value, scriptContext);
+
+            *result = value;
+            return JsNoError;
+        });
+    }
+
     return ContextAPIWrapper<JSRT_MAYBE_TRUE>([&] (Js::ScriptContext *scriptContext, TTDRecorder& _actionEntryPopper) -> JsErrorCode {
         PERFORM_JSRT_TTD_RECORD_ACTION(scriptContext, RecordJsRTVarToStringConversion, (Js::Var)value);
-
         VALIDATE_INCOMING_REFERENCE(value, scriptContext);
-        PARAM_NOT_NULL(result);
-        *result = nullptr;
 
         *result = (JsValueRef) Js::JavascriptConversion::ToString((Js::Var)value, scriptContext);