[counters] Use separate counters for background parsing

src/parsing/parser-base.h

Index: src/parsing/parser-base.h
diff --git a/src/parsing/parser-base.h b/src/parsing/parser-base.h
index 4fe27e2e5a364a79c103051da3159938b991e21a..085d4017a1f81640d5f741e064cf0a3943706a23 100644
--- a/src/parsing/parser-base.h
+++ b/src/parsing/parser-base.h
@@ -192,7 +192,8 @@ class ParserBase {
 
   ParserBase(Zone* zone, Scanner* scanner, uintptr_t stack_limit,
              v8::Extension* extension, AstValueFactory* ast_value_factory,
-             RuntimeCallStats* runtime_call_stats)
+             RuntimeCallStats* runtime_call_stats,
+             bool parsing_on_main_thread = true)
       : scope_state_(nullptr),
         function_state_(nullptr),
         extension_(extension),
@@ -200,6 +201,7 @@ class ParserBase {
         ast_value_factory_(ast_value_factory),
         ast_node_factory_(ast_value_factory),
         runtime_call_stats_(runtime_call_stats),
+        parsing_on_main_thread_(parsing_on_main_thread),
         parsing_module_(false),
         stack_limit_(stack_limit),
         zone_(zone),
@@ -1421,6 +1423,7 @@ class ParserBase {
   AstValueFactory* ast_value_factory_;  // Not owned.
   typename Types::Factory ast_node_factory_;
   RuntimeCallStats* runtime_call_stats_;
+  bool parsing_on_main_thread_;
   bool parsing_module_;
   uintptr_t stack_limit_;
 
@@ -3887,10 +3890,14 @@ template <typename Impl>
 typename ParserBase<Impl>::ExpressionT
 ParserBase<Impl>::ParseArrowFunctionLiteral(
     bool accept_IN, const FormalParametersT& formal_parameters, bool* ok) {
+  const RuntimeCallStats::CounterId counters[2][2] = {
+      {&RuntimeCallStats::ParseArrowFunctionLiteral,
+       &RuntimeCallStats::ParseBackgroundArrowFunctionLiteral},
+      {&RuntimeCallStats::PreParseArrowFunctionLiteral,
+       &RuntimeCallStats::PreParseBackgroundArrowFunctionLiteral}};
   RuntimeCallTimerScope runtime_timer(
       runtime_call_stats_,
-      Impl::IsPreParser() ? &RuntimeCallStats::ParseArrowFunctionLiteral
-                          : &RuntimeCallStats::PreParseArrowFunctionLiteral);
+      counters[Impl::IsPreParser()][parsing_on_main_thread_]);
 
   if (peek() == Token::ARROW && scanner_->HasAnyLineTerminatorBeforeNext()) {
     // ASI inserts `;` after arrow parameters if a line terminator is found.