[counters] Use separate counters for background parsing

src/parsing/preparser.cc

Index: src/parsing/preparser.cc
diff --git a/src/parsing/preparser.cc b/src/parsing/preparser.cc
index 8e5e9ab6525c766804733e3fc4339de452324adf..dc7920d9f523c49959a4d2c1aaddba9063f2abc3 100644
--- a/src/parsing/preparser.cc
+++ b/src/parsing/preparser.cc
@@ -182,8 +182,12 @@ PreParser::Expression PreParser::ParseFunctionLiteral(
   RuntimeCallTimerScope runtime_timer(
       runtime_call_stats_,
       track_unresolved_variables_
-          ? &RuntimeCallStats::PreParseWithVariableResolution
-          : &RuntimeCallStats::PreParseNoVariableResolution);
+          ? parsing_on_main_thread_
+                ? &RuntimeCallStats::PreParseWithVariableResolution
+                : &RuntimeCallStats::PreParseBackgroundWithVariableResolution
+          : parsing_on_main_thread_
+                ? &RuntimeCallStats::PreParseNoVariableResolution
+                : &RuntimeCallStats::PreParseBackgroundNoVariableResolution);
 
   // Parse function body.
   PreParserStatementList body;