Don't assert that no incremental marking happened during a non-incremental GC

src/heap/gc-tracer.cc

Index: src/heap/gc-tracer.cc
diff --git a/src/heap/gc-tracer.cc b/src/heap/gc-tracer.cc
index 6f550aabffa8c59b5865f2f1a02044e6a7005d53..6f3a03f98b3525b4b9ae00af361489125a4f35a7 100644
--- a/src/heap/gc-tracer.cc
+++ b/src/heap/gc-tracer.cc
@@ -218,7 +218,7 @@ void GCTracer::Stop(GarbageCollector collector) {
     DCHECK(current_.incremental_marking_bytes == 0);
     DCHECK(current_.incremental_marking_duration == 0);
     DCHECK(current_.pure_incremental_marking_duration == 0);
-    DCHECK(longest_incremental_marking_step_ == 0.0);
+    longest_incremental_marking_step_ = 0.0;
     mark_compactor_events_.push_front(current_);
   }