Remove global pretenuring mode.

src/heap.h

Index: src/heap.h
diff --git a/src/heap.h b/src/heap.h
index 0101fd6eaa23420236b6c9adf8f267b59d72347c..979b41e77ca1ea2bb8a8c3b9009ca8cfe41b68f8 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -1034,12 +1034,6 @@ class Heap {
   inline int64_t AdjustAmountOfExternalAllocatedMemory(
       int64_t change_in_bytes);
 
-  // Returns the allocation mode (pre-tenuring) based on observed promotion
-  // rates of previous collections.
-  inline PretenureFlag GetPretenureMode() {
-    return FLAG_pretenuring ? TENURED : NOT_TENURED;
-  }
-
   inline intptr_t PromotedTotalSize() {
     int64_t total = PromotedSpaceSizeOfObjects() + PromotedExternalMemorySize();
     if (total > kMaxInt) return static_cast<intptr_t>(kMaxInt);