[heap] Fix SpacesTest.WriteBarrierFromHeapObject

Instead of actually allocating an objects just test the corner cases
around the page boundary by casting addresses.

Bug: v8:7984
Change-Id: I27615cc193d6f85abc91cfe898719a4a9b761f23
Reviewed-on: https://chromium-review.googlesource.com/1151114Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54717}

test/unittests/heap/spaces-unittest.cc

@@ -53,20 +53,18 @@ TEST_F(SpacesTest, CompactionSpaceMerge) {
 }
 
 TEST_F(SpacesTest, WriteBarrierFromHeapObject) {
-  Heap* heap = i_isolate()->heap();
-  CompactionSpace* temporary_space =
-      new CompactionSpace(heap, OLD_SPACE, NOT_EXECUTABLE);
-  EXPECT_NE(nullptr, temporary_space);
-  HeapObject* object =
-      temporary_space->AllocateRawUnaligned(kMaxRegularHeapObjectSize)
-          .ToObjectChecked();
-  EXPECT_NE(nullptr, object);
-
-  MemoryChunk* chunk = MemoryChunk::FromHeapObject(object);
-  heap_internals::MemoryChunk* slim_chunk =
-      heap_internals::MemoryChunk::FromHeapObject(object);
-  EXPECT_EQ(static_cast<void*>(chunk), static_cast<void*>(slim_chunk));
-  delete temporary_space;
+  constexpr Address address1 = Page::kPageSize;
+  HeapObject* object1 = reinterpret_cast<HeapObject*>(address1);
+  MemoryChunk* chunk1 = MemoryChunk::FromHeapObject(object1);
+  heap_internals::MemoryChunk* slim_chunk1 =
+      heap_internals::MemoryChunk::FromHeapObject(object1);
+  EXPECT_EQ(static_cast<void*>(chunk1), static_cast<void*>(slim_chunk1));
+  constexpr Address address2 = 2 * Page::kPageSize - 1;
+  HeapObject* object2 = reinterpret_cast<HeapObject*>(address2);
+  MemoryChunk* chunk2 = MemoryChunk::FromHeapObject(object2);
+  heap_internals::MemoryChunk* slim_chunk2 =
+      heap_internals::MemoryChunk::FromHeapObject(object2);
+  EXPECT_EQ(static_cast<void*>(chunk2), static_cast<void*>(slim_chunk2));
 }
 
 TEST_F(SpacesTest, WriteBarrierIsMarking) {

test/unittests/unittests.status

@@ -3,12 +3,6 @@
 # found in the LICENSE file.
 
 [
-
-[ALWAYS, {
-  # BUG(v8:7984).
-  'SpacesTest.WriteBarrierFromHeapObject': [SKIP],
-}], # ALWAYS
-
 ['system == macos and asan', {
   # BUG(820416).
   'BitsDeathTest*': [SKIP],