Call HeapObjectHeader::checkHeader solely for its side-effect.

This requires changing its signature. This is a preliminary stage to making it
private.

BUG=633030

Review-Url: https://codereview.chromium.org/2698673003
Cr-Commit-Position: refs/heads/master@{#460489}
LargeObjectPage::LargeObjectPage(PageMemory* storage,
                                 BaseArena* arena,
                                 size_t payloadSize)
    : BasePage(storage, arena),
      m_payloadSize(payloadSize)
#if ENABLE(ASAN_CONTAINER_ANNOTATIONS)
      ,
      m_isVectorBackingPage(false)
#endif
{
}

LargeObjectPage::LargeObjectPage(PageMemory* storage,
                                 BaseArena* arena,
                                 size_t payloadSize)
    : BasePage(storage, arena),
      m_payloadSize(payloadSize)
#if ENABLE(ASAN_CONTAINER_ANNOTATIONS)
      ,
      m_isVectorBackingPage(false)
#endif
{
}
