Code:  void assertObjectHasGCInfo(const void* payload, size_t gcInfoIndex) {
  ASSERT(HeapObjectHeader::fromPayload(payload)->checkHeader());
 #if !defined(COMPONENT_BUILD)
  ASSERT(HeapObjectHeader::fromPayload(payload)->gcInfoIndex() == gcInfoIndex);
#endif
}

Commit Message: 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}
CWE ID: CWE-119
 void assertObjectHasGCInfo(const void* payload, size_t gcInfoIndex) {
  HeapObjectHeader::fromPayload(payload)->checkHeader();
 #if !defined(COMPONENT_BUILD)
  ASSERT(HeapObjectHeader::fromPayload(payload)->gcInfoIndex() == gcInfoIndex);
#endif
}
