[heap] Reland move slot filtering logic into sweeper.

test/unittests/heap/slot-set-unittest.cc

Index: test/unittests/heap/slot-set-unittest.cc
diff --git a/test/unittests/heap/slot-set-unittest.cc b/test/unittests/heap/slot-set-unittest.cc
index d24ed1322b4042851cdde1da64611a340b94fc4b..c9b1464d670b48615407aaa7001669030ef342fd 100644
--- a/test/unittests/heap/slot-set-unittest.cc
+++ b/test/unittests/heap/slot-set-unittest.cc
@@ -101,18 +101,21 @@ void CheckRemoveRangeOn(uint32_t start, uint32_t end) {
   set.SetPageStart(0);
   uint32_t first = start == 0 ? 0 : start - kPointerSize;
   uint32_t last = end == Page::kPageSize ? end - kPointerSize : end;
-  for (uint32_t i = first; i <= last; i += kPointerSize) {
-    set.Insert(i);
-  }
-  set.RemoveRange(start, end, SlotSet::FREE_EMPTY_BUCKETS);
-  if (first != start) {
-    EXPECT_TRUE(set.Lookup(first));
-  }
-  if (last == end) {
-    EXPECT_TRUE(set.Lookup(last));
-  }
-  for (uint32_t i = start; i < end; i += kPointerSize) {
-    EXPECT_FALSE(set.Lookup(i));
+  for (const auto mode :
+       {SlotSet::FREE_EMPTY_BUCKETS, SlotSet::KEEP_EMPTY_BUCKETS}) {
+    for (uint32_t i = first; i <= last; i += kPointerSize) {
+      set.Insert(i);
+    }
+    set.RemoveRange(start, end, mode);
+    if (first != start) {
+      EXPECT_TRUE(set.Lookup(first));
+    }
+    if (last == end) {
+      EXPECT_TRUE(set.Lookup(last));
+    }
+    for (uint32_t i = start; i < end; i += kPointerSize) {
+      EXPECT_FALSE(set.Lookup(i));
+    }
   }
 }
 
@@ -134,10 +137,13 @@ TEST(SlotSet, RemoveRange) {
   }
   SlotSet set;
   set.SetPageStart(0);
-  set.Insert(Page::kPageSize / 2);
-  set.RemoveRange(0, Page::kPageSize, SlotSet::FREE_EMPTY_BUCKETS);
-  for (uint32_t i = 0; i < Page::kPageSize; i += kPointerSize) {
-    EXPECT_FALSE(set.Lookup(i));
+  for (const auto mode :
+       {SlotSet::FREE_EMPTY_BUCKETS, SlotSet::KEEP_EMPTY_BUCKETS}) {
+    set.Insert(Page::kPageSize / 2);
+    set.RemoveRange(0, Page::kPageSize, mode);
+    for (uint32_t i = 0; i < Page::kPageSize; i += kPointerSize) {
+      EXPECT_FALSE(set.Lookup(i));
+    }
   }
 }