Revert of [heap] New heuristics for starting of incremental marking.

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 93eba6f150afc5c44a23a21505a4939aa81d5316..9f334f74a1045d44cb8cd20fdf780f32d2b4eb3e 100644
--- a/src/heap/incremental-marking.cc
+++ b/src/heap/incremental-marking.cc
@@ -397,6 +397,22 @@
   for (LargePage* lop : *heap_->lo_space()) {
     SetOldSpacePageFlags(lop, true, is_compacting_);
   }
+}
+
+
+bool IncrementalMarking::ShouldActivateEvenWithoutIdleNotification() {
+#ifndef DEBUG
+  static const intptr_t kActivationThreshold = 8 * MB;
+#else
+  // TODO(gc) consider setting this to some low level so that some
+  // debug tests run with incremental marking and some without.
+  static const intptr_t kActivationThreshold = 0;
+#endif
+  // Don't switch on for very small heaps.
+  return CanBeActivated() &&
+         heap_->PromotedSpaceSizeOfObjects() > kActivationThreshold &&
+         heap_->HeapIsFullEnoughToStartIncrementalMarking(
+             heap_->old_generation_allocation_limit());
 }