Oilpan: trace MediaControlElement's element reference.

Source/core/html/shadow/MediaControlElementTypes.cpp

Index: Source/core/html/shadow/MediaControlElementTypes.cpp
diff --git a/Source/core/html/shadow/MediaControlElementTypes.cpp b/Source/core/html/shadow/MediaControlElementTypes.cpp
index cfd4998beb9490758472f54b5c1765337f2e96c9..b0a51cf0ce8ed0da9460513ae32a1c3927808e8e 100644
--- a/Source/core/html/shadow/MediaControlElementTypes.cpp
+++ b/Source/core/html/shadow/MediaControlElementTypes.cpp
@@ -99,6 +99,11 @@ void MediaControlElement::setDisplayType(MediaControlElementType displayType)
         object->paintInvalidationForWholeRenderer();
 }
 
+void MediaControlElement::trace(Visitor* visitor)
+{
+    visitor->trace(m_element);
+}
+
 // ----------------------------
 
 MediaControlDivElement::MediaControlDivElement(MediaControls& mediaControls, MediaControlElementType displayType)
@@ -107,6 +112,12 @@ MediaControlDivElement::MediaControlDivElement(MediaControls& mediaControls, Med
 {
 }
 
+void MediaControlDivElement::trace(Visitor* visitor)
+{
+    MediaControlElement::trace(visitor);
+    HTMLDivElement::trace(visitor);
+}
+
 // ----------------------------
 
 MediaControlInputElement::MediaControlInputElement(MediaControls& mediaControls, MediaControlElementType displayType)
@@ -120,6 +131,12 @@ bool MediaControlInputElement::isMouseFocusable() const
     return false;
 }
 
+void MediaControlInputElement::trace(Visitor* visitor)
+{
+    MediaControlElement::trace(visitor);
+    HTMLInputElement::trace(visitor);
+}
+
 // ----------------------------
 
 MediaControlTimeDisplayElement::MediaControlTimeDisplayElement(MediaControls& mediaControls, MediaControlElementType displayType)