Revert of [heap] delete Heap::LeftTrimFixedAray

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 3919bdcc2c877f801bb33b36256d622b463cd751..0e5586e95eb6cba0bffe37127e1f9f50a6bac0da 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -835,9 +835,15 @@ class Heap {
   // when introducing gaps within pages.
   void CreateFillerObjectAt(Address addr, int size);
 
+  bool CanMoveObjectStart(HeapObject* object);
+
   // Maintain consistency of live bytes during incremental marking.
   void AdjustLiveBytes(HeapObject* object, int by, InvocationMode mode);
 
+  // Trim the given array from the left. Note that this relocates the object
+  // start and hence is only valid if there is only a single reference to it.
+  FixedArrayBase* LeftTrimFixedArray(FixedArrayBase* obj, int elements_to_trim);
+
   // Trim the given array from the right.
   template<Heap::InvocationMode mode>
   void RightTrimFixedArray(FixedArrayBase* obj, int elements_to_trim);