Introduce infrastructure for tracing ScriptWrappables.

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

Index: third_party/WebKit/Source/platform/heap/HeapPage.h
diff --git a/third_party/WebKit/Source/platform/heap/HeapPage.h b/third_party/WebKit/Source/platform/heap/HeapPage.h
index bb54094a1d36f75d643424a1a8c381a2b14357a1..bcedc4c0c0a1ab095f71e5d22750536f72301e13 100644
--- a/third_party/WebKit/Source/platform/heap/HeapPage.h
+++ b/third_party/WebKit/Source/platform/heap/HeapPage.h
@@ -205,6 +205,9 @@ public:
         ASSERT(size < nonLargeObjectPageSizeMax);
         m_encoded = static_cast<uint32_t>(size) | (m_encoded & ~headerSizeMask);
     }
+    bool isDOMMarked() const;
+    void markDOM();
+    void unmarkDOM();
     bool isMarked() const;
     void mark();
     void unmark();
@@ -835,6 +838,29 @@ inline HeapObjectHeader* HeapObjectHeader::fromPayload(const void* payload)
 }
 
 NO_SANITIZE_ADDRESS inline
+bool HeapObjectHeader::isDOMMarked() const
+{
+    ASSERT(checkHeader());
+    return m_encoded & headerDOMMarkBitMask;
+}
+
+NO_SANITIZE_ADDRESS inline
+void HeapObjectHeader::markDOM()
+{
+    ASSERT(checkHeader());
+    ASSERT(!isDOMMarked());
+    m_encoded |= headerDOMMarkBitMask;
+}
+
+NO_SANITIZE_ADDRESS inline
+void HeapObjectHeader::unmarkDOM()
+{
+    ASSERT(checkHeader());
+    ASSERT(isDOMMarked());
+    m_encoded &= ~headerDOMMarkBitMask;
+}
+
+NO_SANITIZE_ADDRESS inline
 bool HeapObjectHeader::isMarked() const
 {
     ASSERT(checkHeader());