Make incremental marking tracing format consistent with GC tracing.

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 fa22da6d41ecebc06a5f9918c8041e8c10f418dd..ee594b2aee0066390c3fb469583f16d9787b1c67 100644
--- a/src/heap/incremental-marking-inl.h
+++ b/src/heap/incremental-marking-inl.h
@@ -6,6 +6,7 @@
 #define V8_HEAP_INCREMENTAL_MARKING_INL_H_
 
 #include "src/heap/incremental-marking.h"
+#include "src/isolate.h"
 
 namespace v8 {
 namespace internal {
@@ -33,6 +34,15 @@ void IncrementalMarking::RecordWriteIntoCode(Code* host, RelocInfo* rinfo,
   }
 }
 
+void IncrementalMarking::RestartIfNotMarking() {
+  if (state_ == COMPLETE) {
+    state_ = MARKING;
+    if (FLAG_trace_incremental_marking) {
+      heap()->isolate()->PrintWithTimestamp(
+          "[IncrementalMarking] Restarting (new grey objects)\n");
+    }
+  }
+}
 
 }  // namespace internal
 }  // namespace v8