Use the Oilpan heap canary only on 64-bit.

third_party/WebKit/Source/platform/heap/HeapPage.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 70 matching lines @@
     static_cast<LargeObjectPage*>(largePage)->setIsVectorBackingPage(); \
   }
 #else
 #define ENABLE_ASAN_CONTAINER_ANNOTATIONS 0
 #define ASAN_RETIRE_CONTAINER_ANNOTATION(payload, payloadSize)
 #define ASAN_MARK_LARGE_VECTOR_CONTAINER(arena, largeObject)
 #endif
 
 namespace blink {
 
-#if DCHECK_IS_ON()
+#if DCHECK_IS_ON() && CPU(64BIT)
 NO_SANITIZE_ADDRESS
 void HeapObjectHeader::zapMagic() {
   ASSERT(checkHeader());
   m_magic = zappedMagic;
 }
 #endif
 
 void HeapObjectHeader::finalize(Address object, size_t objectSize) {
   HeapAllocHooks::freeHookIfEnabled(object);
   const GCInfo* gcInfo = ThreadHeap::gcInfo(gcInfoIndex());
@@ skipping 1724 matching lines @@
 
   m_hasEntries = true;
   size_t index = hash(address);
   ASSERT(!(index & 1));
   Address cachePage = roundToBlinkPageStart(address);
   m_entries[index + 1] = m_entries[index];
   m_entries[index] = cachePage;
 }
 
 }  // namespace blink