[GC] Remove FLAG_incremental_marking_steps

BUG=

Review URL: https://codereview.chromium.org/1281923002

Cr-Commit-Position: refs/heads/master@{#30083}

src/flag-definitions.h

@@ -636,7 +636,6 @@ DEFINE_BOOL(age_code, true,
             "track un-executed functions to age code and flush only "
             "old code (required for code flushing)")
 DEFINE_BOOL(incremental_marking, true, "use incremental marking")
-DEFINE_BOOL(incremental_marking_steps, true, "do incremental marking steps")
 DEFINE_BOOL(overapproximate_weak_closure, true,
             "overapproximate weak closer to reduce atomic pause time")
 DEFINE_INT(min_progress_during_object_groups_marking, 128,

src/heap/heap.cc

@@ -896,8 +896,7 @@ bool Heap::CollectGarbage(GarbageCollector collector, const char* gc_reason,
       !mark_compact_collector()->finalize_incremental_marking() &&
       !mark_compact_collector()->abort_incremental_marking() &&
       !incremental_marking()->IsStopped() &&
-      !incremental_marking()->should_hurry() &&
-      FLAG_incremental_marking_steps) {
+      !incremental_marking()->should_hurry() && FLAG_incremental_marking) {
     // Make progress in incremental marking.
     const intptr_t kStepSizeWhenDelayedByScavenge = 1 * MB;
     incremental_marking()->Step(kStepSizeWhenDelayedByScavenge,

src/heap/incremental-marking.cc

@@ -411,8 +411,7 @@ bool IncrementalMarking::CanBeActivated() {
   // marking is turned on, 2) when we are currently not in a GC, and
   // 3) when we are currently not serializing or deserializing the heap.
   // Don't switch on for very small heaps.
-  return FLAG_incremental_marking && FLAG_incremental_marking_steps &&
-         heap_->gc_state() == Heap::NOT_IN_GC &&
+  return FLAG_incremental_marking && heap_->gc_state() == Heap::NOT_IN_GC &&
          heap_->deserialization_complete() &&
          !heap_->isolate()->serializer_enabled() &&
          heap_->PromotedSpaceSizeOfObjects() > kActivationThreshold;
@@ -478,7 +477,6 @@ void IncrementalMarking::Start(int mark_compact_flags,
            (reason == nullptr) ? "unknown reason" : reason);
   }
   DCHECK(FLAG_incremental_marking);
-  DCHECK(FLAG_incremental_marking_steps);
   DCHECK(state_ == STOPPED);
   DCHECK(heap_->gc_state() == Heap::NOT_IN_GC);
   DCHECK(!heap_->isolate()->serializer_enabled());
@@ -912,7 +910,6 @@ intptr_t IncrementalMarking::Step(intptr_t allocated_bytes,
                                   ForceMarkingAction marking,
                                   ForceCompletionAction completion) {
   if (heap_->gc_state() != Heap::NOT_IN_GC || !FLAG_incremental_marking ||
-      !FLAG_incremental_marking_steps ||
       (state_ != SWEEPING && state_ != MARKING)) {
     return 0;
   }

src/heap/spaces.cc

@@ -2407,7 +2407,7 @@ HeapObject* FreeList::Allocate(int size_in_bytes) {
     DCHECK(owner_->top() == NULL && owner_->limit() == NULL);
   } else if (bytes_left > kThreshold &&
              owner_->heap()->incremental_marking()->IsMarkingIncomplete() &&
-             FLAG_incremental_marking_steps) {
+             FLAG_incremental_marking) {
     int linear_size = owner_->RoundSizeDownToObjectAlignment(kThreshold);
     // We don't want to give too large linear areas to the allocator while
     // incremental marking is going on, because we won't check again whether