[cleanup] Remove MemoryChunk::kOwnerOffset

kOwnerOffset is redundant after 8a437788
since we check the READ_ONLY_HEAP bit instead of MemoryChunk::owner_ in
heap-write-barrier-inl.h

Bug: v8:9183
Change-Id: Ia0fbb530c088b8a87c551a99cc29d8cf7bd118f5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1664341Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Maciej Goszczycki <goszczycki@google.com>
Auto-Submit: Maciej Goszczycki <goszczycki@google.com>
Cr-Commit-Position: refs/heads/master@{#62253}

src/heap/spaces.cc

@@ -744,7 +744,6 @@ MemoryChunk* MemoryChunk::Initialize(Heap* heap, Address base, size_t size,
 
   DCHECK_EQ(kFlagsOffset, OFFSET_OF(MemoryChunk, flags_));
   DCHECK_EQ(kHeapOffset, OFFSET_OF(MemoryChunk, heap_));
-  DCHECK_EQ(kOwnerOffset, OFFSET_OF(MemoryChunk, owner_));
 
   if (executable == EXECUTABLE) {
     chunk->SetFlag(IS_EXECUTABLE);

src/heap/spaces.h

@@ -392,8 +392,6 @@ class MemoryChunk {
       kReservationOffset + 3 * kSystemPointerSize;
   static const intptr_t kHeaderSentinelOffset =
       kHeapOffset + kSystemPointerSize;
-  static const intptr_t kOwnerOffset =
-      kHeaderSentinelOffset + kSystemPointerSize;
 
   static const size_t kHeaderSize =
       kSizeOffset               // NOLINT