Print PID and isolate address in gc traces.

src/utils.h

Index: src/utils.h
diff --git a/src/utils.h b/src/utils.h
index 070ae7cabebaec1aaa2b456d6773115361651716..dbb80e752234c706041ec56978ce85060c9f4315 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -1140,6 +1140,9 @@ void FPRINTF_CHECKING PrintF(FILE* out, const char* format, ...);
 // Prepends the current process ID to the output.
 void PRINTF_CHECKING PrintPID(const char* format, ...);
 
+// Prepends the current process ID and given isolate pointer to the output.
+void PrintIsolate(void* isolate, const char* format, ...);
+
 // Safe formatting print. Ensures that str is always null-terminated.
 // Returns the number of chars written, or -1 if output was truncated.
 int FPRINTF_CHECKING SNPrintF(Vector<char> str, const char* format, ...);