Add more checks to diagnose MediaQuerySet issue

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

 /*
  * 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 223 matching lines @@
 
   void Finalize(Address, size_t);
   static HeapObjectHeader* FromPayload(const void*);
 
   // Some callers formerly called |fromPayload| only for its side-effect of
   // calling |checkHeader| (which is now private). This function does that, but
   // its explanatory name makes the intention at the call sites easier to
   // understand, and is public.
   static void CheckFromPayload(const void*);
 
+  // Returns true if magic number is valid.
+  bool IsValid() const;
+
   static const uint32_t kZappedMagic = 0xDEAD4321;
 
  protected:
 #if DCHECK_IS_ON() && CPU(64BIT)
   // Zap |m_magic| with a new magic number that means there was once an object
   // allocated here, but it was freed because nobody marked it during GC.
   void ZapMagic();
 #endif
 
  private:
@@ skipping 593 matching lines @@
 
 NO_SANITIZE_ADDRESS inline size_t HeapObjectHeader::size() const {
   size_t result = encoded_ & kHeaderSizeMask;
   // Large objects should not refer to header->size(). The actual size of a
   // large object is stored in |LargeObjectPage::m_payloadSize|.
   DCHECK(result != kLargeObjectSizeInHeader);
   DCHECK(!PageFromObject(this)->IsLargeObjectPage());
   return result;
 }
 
+NO_SANITIZE_ADDRESS inline bool HeapObjectHeader::IsValid() const {
+#if CPU(64BIT)
+  return GetMagic() == magic_;
+#else
+  return true;
+#endif
+}
+
 NO_SANITIZE_ADDRESS inline void HeapObjectHeader::CheckHeader() const {
 #if CPU(64BIT)
-  const bool good_magic = GetMagic() == magic_;
-  DCHECK(good_magic);
+  DCHECK(IsValid());
 #endif
 }
 
 inline Address HeapObjectHeader::Payload() {
   return reinterpret_cast<Address>(this) + sizeof(HeapObjectHeader);
 }
 
 inline Address HeapObjectHeader::PayloadEnd() {
   return reinterpret_cast<Address>(this) + size();
 }
@@ skipping 131 matching lines @@
   return OutOfLineAllocate(allocation_size, gc_info_index);
 }
 
 inline NormalPageArena* NormalPage::ArenaForNormalPage() const {
   return static_cast<NormalPageArena*>(Arena());
 }
 
 }  // namespace blink
 
 #endif  // HeapPage_h