Revert of [heap] Remove border page

src/heap/heap-inl.h

Index: src/heap/heap-inl.h
diff --git a/src/heap/heap-inl.h b/src/heap/heap-inl.h
index dda9a89c988b47349b26d07b7920064d76a82c58..9499546850e55f5133daecb1286a52faadcdcb96 100644
--- a/src/heap/heap-inl.h
+++ b/src/heap/heap-inl.h
@@ -519,6 +519,9 @@
 
 template <PromotionMode promotion_mode>
 bool Heap::ShouldBePromoted(Address old_address, int object_size) {
+  Page* page = Page::FromAddress(old_address);
+  Address age_mark = new_space_->age_mark();
+
   if (promotion_mode == PROMOTE_MARKED) {
     MarkBit mark_bit = ObjectMarking::MarkBitFrom(old_address);
     if (!Marking::IsWhite(mark_bit)) {
@@ -526,7 +529,8 @@
     }
   }
 
-  return Page::FromAddress(old_address)->InIntermediateGeneration();
+  return page->IsFlagSet(MemoryChunk::NEW_SPACE_BELOW_AGE_MARK) &&
+         (!page->ContainsLimit(age_mark) || old_address < age_mark);
 }
 
 PromotionMode Heap::CurrentPromotionMode() {
@@ -627,8 +631,16 @@
   // Bail out if the memento is below the age mark, which can happen when
   // mementos survived because a page got moved within new space.
   Page* object_page = Page::FromAddress(object_address);
-  if (object_page->InIntermediateGeneration()) {
-    return nullptr;
+  if (object_page->IsFlagSet(Page::NEW_SPACE_BELOW_AGE_MARK)) {
+    Address age_mark =
+        reinterpret_cast<SemiSpace*>(object_page->owner())->age_mark();
+    if (!object_page->Contains(age_mark)) {
+      return nullptr;
+    }
+    // Do an exact check in the case where the age mark is on the same page.
+    if (object_address < age_mark) {
+      return nullptr;
+    }
   }
 
   AllocationMemento* memento_candidate = AllocationMemento::cast(candidate);