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..9b1443131a982a0ffc670b60553e18afc4b1cb26 100644
--- a/third_party/WebKit/Source/platform/heap/HeapPage.h
+++ b/third_party/WebKit/Source/platform/heap/HeapPage.h
@@ -142,7 +142,7 @@ class WebMemoryAllocatorDump;
 // - 1 bit used to mark DOM trees for V8.
 // - 14 bit is enough for gcInfoIndex because there are less than 2^14 types
 //   in Blink.
-const size_t headerDOMMarkBitMask = 1u << 17;
+const size_t headerWrapperMarkBitMask = 1u << 17;
 const size_t headerGCInfoIndexShift = 18;
 const size_t headerGCInfoIndexMask = (static_cast<size_t>((1 << 14) - 1)) << headerGCInfoIndexShift;
 const size_t headerSizeMask = (static_cast<size_t>((1 << 14) - 1)) << 3;
@@ -205,6 +205,9 @@ public:
         ASSERT(size < nonLargeObjectPageSizeMax);
         m_encoded = static_cast<uint32_t>(size) | (m_encoded & ~headerSizeMask);
     }
+    bool isWrapperHeaderMarked() const;
+    void markWrapperHeader();
+    void unmarkWrapperHeader();
     bool isMarked() const;
     void mark();
     void unmark();
@@ -835,6 +838,29 @@ inline HeapObjectHeader* HeapObjectHeader::fromPayload(const void* payload)
 }
 
 NO_SANITIZE_ADDRESS inline
+bool HeapObjectHeader::isWrapperHeaderMarked() const
+{
+    ASSERT(checkHeader());
+    return m_encoded & headerWrapperMarkBitMask;
+}
+
+NO_SANITIZE_ADDRESS inline
+void HeapObjectHeader::markWrapperHeader()
+{
+    ASSERT(checkHeader());
+    ASSERT(!isWrapperHeaderMarked());
+    m_encoded |= headerWrapperMarkBitMask;
+}
+
+NO_SANITIZE_ADDRESS inline
+void HeapObjectHeader::unmarkWrapperHeader()
+{
+    ASSERT(checkHeader());
+    ASSERT(isWrapperHeaderMarked());
+    m_encoded &= ~headerWrapperMarkBitMask;
+}
+
+NO_SANITIZE_ADDRESS inline
 bool HeapObjectHeader::isMarked() const
 {
     ASSERT(checkHeader());