Add OS::GetCurrentProcessId and prepend output from trace-gc with the current pid

src/v8utils.cc

 // Copyright 2011 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 35 matching lines @@
 
 
 void PrintF(FILE* out, const char* format, ...) {
   va_list arguments;
   va_start(arguments, format);
   OS::VFPrint(out, format, arguments);
   va_end(arguments);
 }
 
 
+void PrintPID(const char* format, ...) {
+  OS::Print("[%d] ", OS::GetCurrentProcessId());
+  va_list arguments;
+  va_start(arguments, format);
+  OS::VPrint(format, arguments);
+  va_end(arguments);
+}
+
+
 void Flush(FILE* out) {
   fflush(out);
 }
 
 
 char* ReadLine(const char* prompt) {
   char* result = NULL;
   char line_buf[256];
   int offset = 0;
   bool keep_going = true;
@@ skipping 285 matching lines @@
       start_of_line = p;
       line_no++;
     }
   }
 
   return is_ascii;
 }
 
 
 } }  // namespace v8::internal