[heap] Initialize the owner on each page after lospace allocation

src/heap/spaces.h

Index: src/heap/spaces.h
diff --git a/src/heap/spaces.h b/src/heap/spaces.h
index 68ef25d9a1977253f6985a1c4e42efd4654beee8..c97efd5a1e9edce8570672bf8a7c394bb439bc87 100644
--- a/src/heap/spaces.h
+++ b/src/heap/spaces.h
@@ -317,8 +317,11 @@ class MemoryChunk {
   static const intptr_t kAlignmentMask = kAlignment - 1;
 
   static const intptr_t kSizeOffset = 0;
-
-  static const intptr_t kFlagsOffset = kSizeOffset + kPointerSize;
+  static const intptr_t kFlagsOffset = kSizeOffset + kSizetSize;
+  static const intptr_t kAreaStartOffset = kFlagsOffset + kIntptrSize;
+  static const intptr_t kAreaEndOffset = kAreaStartOffset + kPointerSize;
+  static const intptr_t kReservationOffset = kAreaEndOffset + kPointerSize;
+  static const intptr_t kOwnerOffset = kReservationOffset + 2 * kPointerSize;
 
   static const size_t kMinHeaderSize =
       kSizeOffset + kSizetSize  // size_t size