[counters] Use separate counters for background parsing

src/parsing/preparser.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_PARSING_PREPARSER_H
 #define V8_PARSING_PREPARSER_H
 
 #include "src/ast/scopes.h"
 #include "src/parsing/parser-base.h"
 
@@ skipping 820 matching lines @@
   typedef PreParserIdentifier Identifier;
   typedef PreParserExpression Expression;
   typedef PreParserStatement Statement;
 
   enum PreParseResult {
     kPreParseStackOverflow,
     kPreParseAbort,
     kPreParseSuccess
   };
 
-  PreParser(Zone* zone, Scanner* scanner, AstValueFactory* ast_value_factory,
+  PreParser(Zone* zone, Scanner* scanner, uintptr_t stack_limit,
+            AstValueFactory* ast_value_factory,
             PendingCompilationErrorHandler* pending_error_handler,
-            RuntimeCallStats* runtime_call_stats, uintptr_t stack_limit)
+            RuntimeCallStats* runtime_call_stats,
+            bool parsing_on_main_thread = true)
       : ParserBase<PreParser>(zone, scanner, stack_limit, nullptr,
-                              ast_value_factory, runtime_call_stats),
+                              ast_value_factory, runtime_call_stats,
+                              parsing_on_main_thread),
         use_counts_(nullptr),
         track_unresolved_variables_(false),
         pending_error_handler_(pending_error_handler) {}
 
   static bool const IsPreParser() { return true; }
 
   PreParserLogger* logger() { return &log_; }
 
   // Pre-parse the program from the character stream; returns true on
   // success (even if parsing failed, the pre-parse data successfully
@@ skipping 701 matching lines @@
     function_state_->NextMaterializedLiteralIndex();
     function_state_->NextMaterializedLiteralIndex();
   }
   return EmptyExpression();
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PREPARSER_H