Fix Heap::AllocateFillerObject() to use double alignment param.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 1ccdf3b4a51f7d88e7b0f0a3303ebb06b95fe64e..181bc2ca78232f440fdafeccf89e1f346fd0dbcf 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -2534,7 +2534,8 @@ AllocationResult Heap::AllocateFillerObject(int size, bool double_align,
                                             AllocationSpace space) {
   HeapObject* obj;
   {
-    AllocationResult allocation = AllocateRaw(size, space, space);
+    AllocationAlignment align = double_align ? kDoubleAligned : kWordAligned;
+    AllocationResult allocation = AllocateRaw(size, space, space, align);
     if (!allocation.To(&obj)) return allocation;
   }
 #ifdef DEBUG