[heap] Check for --track_retaining_path in incremental marking visitor

This removes the usage of retaining_path_mode template parameter in
main thread marking visitor and makes the incremental visitor
identical to the stop-the-world visitor.

Subsequent CL will switch these visitors to MarkingVisitorBase.

Bug: chromium:1019218
Change-Id: I00e3ef190d8f2ac821cb63b02c402aad5ea49e9c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1897538Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64757}

src/heap/mark-compact-inl.h

@@ -338,8 +338,7 @@ void MarkingVisitor<fixed_array_mode, retaining_path_mode, MarkingState>::
   // descriptor array is grey. So we need to do two steps: WhiteToGrey and
   // GreyToBlack. Alternatively, we could check WhiteToGrey || WhiteToBlack.
   if (marking_state()->WhiteToGrey(descriptors)) {
-    if (retaining_path_mode == TraceRetainingPathMode::kEnabled &&
-        V8_UNLIKELY(FLAG_track_retaining_path)) {
+    if (V8_UNLIKELY(FLAG_track_retaining_path)) {
       heap_->AddRetainer(host, descriptors);
     }
   }
@@ -357,8 +356,7 @@ void MarkingVisitor<fixed_array_mode, retaining_path_mode,
                                               HeapObject object) {
   if (marking_state()->WhiteToGrey(object)) {
     marking_worklist()->Push(object);
-    if (retaining_path_mode == TraceRetainingPathMode::kEnabled &&
-        V8_UNLIKELY(FLAG_track_retaining_path)) {
+    if (V8_UNLIKELY(FLAG_track_retaining_path)) {
       heap_->AddRetainer(host, object);
     }
   }