Oilpan: Trace VTTParser::m_document.

BUG=357163

Review URL: https://codereview.chromium.org/336323002

git-svn-id: svn://svn.chromium.org/blink/trunk@176273 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/html/track/vtt/VTTParser.cpp

@@ -561,6 +561,7 @@ void VTTTreeBuilder::constructTreeFromToken(Document& document)
 
 void VTTParser::trace(Visitor* visitor)
 {
+    visitor->trace(m_document);
     visitor->trace(m_cueList);
     visitor->trace(m_regionList);
 }

third_party/WebKit/Source/core/html/track/vtt/VTTParser.h

@@ -113,7 +113,7 @@ public:
 private:
     VTTParser(VTTParserClient*, Document&);
 
-    Document* m_document;
+    RawPtrWillBeMember<Document> m_document;
     ParseState m_state;
 
     void parse();