Move EmbedderHeapTracer::TracePrologue call to the beginning of full gc

src/heap/incremental-marking.cc

Index: src/heap/incremental-marking.cc
diff --git a/src/heap/incremental-marking.cc b/src/heap/incremental-marking.cc
index 35b8508472ad2ed8b2fbbf5d06910c3d74228761..bc8ade9c44948dfda52256efa7181e12a6aa9f24 100644
--- a/src/heap/incremental-marking.cc
+++ b/src/heap/incremental-marking.cc
@@ -542,6 +542,10 @@ void IncrementalMarking::StartMarking() {
 
   state_ = MARKING;
 
+  if (heap_->UsingEmbedderHeapTracer()) {
+    heap_->mark_compact_collector()->embedder_heap_tracer()->TracePrologue();
+  }
+
   RecordWriteStub::Mode mode = is_compacting_
                                    ? RecordWriteStub::INCREMENTAL_COMPACTION
                                    : RecordWriteStub::INCREMENTAL;