Oilpan: Fix weak processing for IntersectionObserver::m_root

third_party/WebKit/Source/core/dom/IntersectionObserver.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/dom/IntersectionObserver.h"
 
 #include "bindings/core/v8/ExceptionState.h"
 #include "core/css/parser/CSSParserTokenRange.h"
 #include "core/css/parser/CSSTokenizer.h"
 #include "core/dom/ExceptionCode.h"
@@ skipping 299 matching lines @@
 }
 
 bool IntersectionObserver::hasPercentMargin() const
 {
     return (m_topMargin.type() == Percent
         || m_rightMargin.type() == Percent
         || m_bottomMargin.type() == Percent
         || m_leftMargin.type() == Percent);
 }
 
-void IntersectionObserver::rootDisappearedCallback(Visitor* visitor, void* self)
+void IntersectionObserver::clearWeakMembers(Visitor* visitor)
 {
-    IntersectionObserver* observer = static_cast<IntersectionObserver*>(self);
-    observer->disconnect();
+    if (Heap::isHeapObjectAlive(m_root))
+        return;
+    disconnect();
+    m_root = nullptr;
 }
 
 DEFINE_TRACE(IntersectionObserver)
 {
 #if ENABLE(OILPAN)
-    visitor->registerWeakMembers(this, m_root.get(), IntersectionObserver::rootDisappearedCallback);
+    visitor->template registerWeakMembers<IntersectionObserver, &IntersectionObserver::clearWeakMembers>(this);
 #endif
     visitor->trace(m_callback);
-    visitor->trace(m_root);
     visitor->trace(m_observations);
     visitor->trace(m_entries);
 }
 
 } // namespace blink