Ensure synchronized access to the perf dump file.

src/perf-jit.h

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 69 matching lines @@
 #elif V8_TARGET_ARCH_ARM
     return kElfMachARM;
 #elif V8_TARGET_ARCH_MIPS
     return kElfMachMIPS;
 #else
     UNIMPLEMENTED();
     return 0;
 #endif
   }
 
-  FILE* perf_output_handle_;
-  uint64_t code_index_;
-  void* marker_address_;
+  // Per-process singleton file. We assume that there is one main isolate;
+  // to determine when it goes away, we keep reference count.
+  static base::LazyRecursiveMutex file_mutex_;
+  static FILE* perf_output_handle_;
+  static uint64_t reference_count_;
+  static void* marker_address_;
+  static uint64_t code_index_;
 };
 
 #else
 
 // PerfJitLogger is only implemented on Linux
 class PerfJitLogger : public CodeEventLogger {
  public:
   void CodeMoveEvent(AbstractCode* from, Address to) override {
     UNIMPLEMENTED();
   }
 
   void CodeDisableOptEvent(AbstractCode* code,
                            SharedFunctionInfo* shared) override {
     UNIMPLEMENTED();
   }
 
   void LogRecordedBuffer(AbstractCode* code, SharedFunctionInfo* shared,
                          const char* name, int length) override {
     UNIMPLEMENTED();
   }
 };
 
 #endif  // V8_OS_LINUX
 }  // namespace internal
 }  // namespace v8
 #endif