Oilpan: Trace MediaQueryMacher::m_document.

BUG=357163

Review URL: https://codereview.chromium.org/331283004

git-svn-id: svn://svn.chromium.org/blink/trunk@176275 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/css/MediaQueryMatcher.cpp

@@ -61,7 +61,7 @@ DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(MediaQueryMatcher)
 void MediaQueryMatcher::documentDestroyed()
 {
     m_listeners.clear();
-    m_document = 0;
+    m_document = nullptr;
 }
 
 AtomicString MediaQueryMatcher::mediaType() const
@@ -142,6 +142,7 @@ void MediaQueryMatcher::styleResolverChanged()
 
 void MediaQueryMatcher::trace(Visitor* visitor)
 {
+    visitor->trace(m_document);
     // We don't support tracing of vectors of OwnPtrs (ie. Vector<OwnPtr<Listener> >).
     // Since this is a transitional object we are just ifdef'ing it out when oilpan is not enabled.
 #if ENABLE(OILPAN)

third_party/WebKit/Source/core/css/MediaQueryMatcher.h

@@ -75,7 +75,7 @@ private:
     PassOwnPtr<MediaQueryEvaluator> prepareEvaluator() const;
     AtomicString mediaType() const;
 
-    Document* m_document;
+    RawPtrWillBeMember<Document> m_document;
     WillBeHeapVector<OwnPtrWillBeMember<Listener> > m_listeners;
 
     // This value is incremented at style selector changes.