GC: Refactor public incremental marking interface in heap

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 750827968dcd757edff47ece2ed0948930aa688f..eae80d1d66c79b24c745d126eb19eaee95875554 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -852,6 +852,21 @@ class Heap {
   // incremental steps.
   void StartIdleIncrementalMarking();
 
+  // Starts incremental marking assuming incremental marking is currently
+  // stopped.
+  void StartIncrementalMarking(int gc_flags,
+                               const GCCallbackFlags gc_callback_flags,
+                               const char* reason = nullptr);
+
+  // Performs incremental marking steps of step_size_in_bytes as long as
+  // deadline_ins_ms is not reached. step_size_in_bytes can be 0 to compute
+  // an estimate increment. Returns the remaining time that cannot be used
+  // for incremental marking anymore because a single step would exceed the
+  // deadline.
+  double AdvanceIncrementalMarking(
+      intptr_t step_size_in_bytes, double deadline_in_ms,
+      IncrementalMarking::StepActions step_actions);
+
   inline void increment_scan_on_scavenge_pages() {
     scan_on_scavenge_pages_++;
     if (FLAG_gc_verbose) {
@@ -2232,10 +2247,6 @@ class Heap {
 
   GCIdleTimeHandler::HeapState ComputeHeapState();
 
-  double AdvanceIncrementalMarking(
-      intptr_t step_size_in_bytes, double deadline_in_ms,
-      IncrementalMarking::ForceCompletionAction completion);
-
   bool PerformIdleTimeAction(GCIdleTimeAction action,
                              GCIdleTimeHandler::HeapState heap_state,
                              double deadline_in_ms);