GC: Refactor public incremental marking interface in heap

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 947c961af8993d6efc959d4d1c7765a1c2e352a1..f9b7319eb0cfab1a080893f0996967a87d0ee3b2 100644
--- a/src/heap/incremental-marking.cc
+++ b/src/heap/incremental-marking.cc
@@ -16,6 +16,13 @@ namespace v8 {
 namespace internal {
 
 
+IncrementalMarking::StepActions IncrementalMarking::NoForcedStepActions() {
+  return StepActions(IncrementalMarking::NO_GC_VIA_STACK_GUARD,
+                     IncrementalMarking::DO_NOT_FORCE_MARKING,
+                     IncrementalMarking::DO_NOT_FORCE_COMPLETION);
+}
+
+
 IncrementalMarking::IncrementalMarking(Heap* heap)
     : heap_(heap),
       state_(STOPPED),
@@ -470,9 +477,12 @@ static void PatchIncrementalMarkingRecordWriteStubs(
 }
 
 
-void IncrementalMarking::Start(int mark_compact_flags) {
+void IncrementalMarking::Start(int mark_compact_flags,
+                               const GCCallbackFlags gc_callback_flags,
+                               const char* reason) {
   if (FLAG_trace_incremental_marking) {
-    PrintF("[IncrementalMarking] Start\n");
+    PrintF("[IncrementalMarking] Start (%s)\n",
+           (reason == nullptr) ? "unknown reason" : reason);
   }
   DCHECK(FLAG_incremental_marking);
   DCHECK(FLAG_incremental_marking_steps);
@@ -482,6 +492,7 @@ void IncrementalMarking::Start(int mark_compact_flags) {
 
   ResetStepCounters();
 
+  gc_callback_flags_ = gc_callback_flags;
   was_activated_ = true;
 
   if (!heap_->mark_compact_collector()->sweeping_in_progress()) {
@@ -824,7 +835,7 @@ void IncrementalMarking::Epilogue() {
 
 void IncrementalMarking::OldSpaceStep(intptr_t allocated) {
   if (IsStopped() && ShouldActivateEvenWithoutIdleNotification()) {
-    Start(Heap::kNoGCFlags);
+    Start(Heap::kNoGCFlags, kNoGCCallbackFlags, "old space step");
   } else {
     Step(allocated * kFastMarking / kInitialMarkingSpeed, GC_VIA_STACK_GUARD);
   }