Revert of Use a slot that is located on a heap page when removing invalid entries from the SlotsBuffer.

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index 489b92aca987fd251128e262404e03baafbeaa41..b4fafec10939aea23ddd4bc2aada41fee52eced9 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -4558,14 +4558,14 @@
 }
 
 
+static Object* g_smi_slot = NULL;
+
+
 void SlotsBuffer::RemoveInvalidSlots(Heap* heap, SlotsBuffer* buffer) {
-  // Remove entries by replacing them with an old-space slot containing a smi
-  // that is located in an unmovable page.
-  const ObjectSlot kRemovedEntry =
-      HeapObject::RawField(heap->empty_fixed_array(),
-                           FixedArrayBase::kLengthOffset);
-  DCHECK(Page::FromAddress(
-      reinterpret_cast<Address>(kRemovedEntry))->NeverEvacuate());
+  DCHECK_EQ(Smi::FromInt(0), g_smi_slot);
+
+  // Remove entries by replacing them with a dummy slot containing a smi.
+  const ObjectSlot kRemovedEntry = &g_smi_slot;
 
   while (buffer != NULL) {
     SlotsBuffer::ObjectSlot* slots = buffer->slots_;
@@ -4593,6 +4593,8 @@
 
 
 void SlotsBuffer::VerifySlots(Heap* heap, SlotsBuffer* buffer) {
+  DCHECK_EQ(Smi::FromInt(0), g_smi_slot);
+
   while (buffer != NULL) {
     SlotsBuffer::ObjectSlot* slots = buffer->slots_;
     intptr_t slots_count = buffer->idx_;