[heap] Remove obsolete owner field initialization code.

Change-Id: I66426ab06f8cc3f138a9cdd60063a3da1dc4a954
Reviewed-on: https://chromium-review.googlesource.com/1123824Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54163}

src/heap/spaces.cc

@@ -720,13 +720,6 @@ LargePage* LargePage::Initialize(Heap* heap, MemoryChunk* chunk,
 
   MSAN_ALLOCATED_UNINITIALIZED_MEMORY(chunk->area_start(), chunk->area_size());
 
-  // Initialize the owner field for each contained page (except the first, which
-  // is initialized by MemoryChunk::Initialize).
-  for (Address addr = chunk->address() + Page::kPageSize + Page::kOwnerOffset;
-       addr < chunk->area_end(); addr += Page::kPageSize) {
-    // Clear out kPageHeaderTag.
-    Memory::Address_at(addr) = 0;
-  }
   LargePage* page = static_cast<LargePage*>(chunk);
   page->list_node().Initialize();
   page->InitializationMemoryFence();