Print PID and isolate address in gc traces.

src/heap/incremental-marking-inl.h

Index: src/heap/incremental-marking-inl.h
diff --git a/src/heap/incremental-marking-inl.h b/src/heap/incremental-marking-inl.h
index 496e02d9550b16cc16c7110e99dd24d7253c89d3..42b3dcb127da27fc1ebd937912c43580735dd596 100644
--- a/src/heap/incremental-marking-inl.h
+++ b/src/heap/incremental-marking-inl.h
@@ -96,8 +96,10 @@ void IncrementalMarking::BlackToGreyAndUnshift(HeapObject* obj,
       // as the program mutates the heap faster than we can incrementally
       // trace it.  In this case we switch to non-incremental marking in
       // order to finish off this marking phase.
-      if (FLAG_trace_gc) {
-        PrintPID("Hurrying incremental marking because of lack of progress\n");
+      if (FLAG_trace_incremental_marking) {
+        PrintIsolate(
+            heap()->isolate(),
+            "Hurrying incremental marking because of lack of progress\n");
       }
       marking_speed_ = kMaxMarkingSpeed;
     }