Oilpan: tidy up AutoplayExperimentHelper.

third_party/WebKit/Source/core/html/AutoplayExperimentHelper.h

Index: third_party/WebKit/Source/core/html/AutoplayExperimentHelper.h
diff --git a/third_party/WebKit/Source/core/html/AutoplayExperimentHelper.h b/third_party/WebKit/Source/core/html/AutoplayExperimentHelper.h
index 9b66a91142a6decbb85ab56cafa34206f4e0663e..a35406017692312b1c2aab08fc8c726e0ca14326 100644
--- a/third_party/WebKit/Source/core/html/AutoplayExperimentHelper.h
+++ b/third_party/WebKit/Source/core/html/AutoplayExperimentHelper.h
@@ -67,9 +67,10 @@ enum AutoplayMetrics {
     NumberOfAutoplayMetrics,
 };
 
-class AutoplayExperimentHelper {
+class AutoplayExperimentHelper final {
+    DISALLOW_NEW_EXCEPT_PLACEMENT_NEW();
 public:
-    AutoplayExperimentHelper(HTMLMediaElement&);
+    explicit AutoplayExperimentHelper(HTMLMediaElement&);
     ~AutoplayExperimentHelper();
 
     void becameReadyToPlay();
@@ -103,6 +104,11 @@ public:
         PlayMuted     = 1 << 6,
     };
 
+    DEFINE_INLINE_TRACE()
+    {
+        visitor->trace(m_element);
+    }
+
 private:
     // Register to receive position updates, if we haven't already.  If we
     // have, then this does nothing.
@@ -139,6 +145,8 @@ private:
     // Return our media element's document.
     Document& document() const;
 
+    HTMLMediaElement& element() const;
+
     inline bool enabled(Mode mode) const
     {
         return ((int)m_mode) & ((int)mode);
@@ -146,8 +154,7 @@ private:
 
     Mode fromString(const String& mode);
 
-private:
-    HTMLMediaElement& m_element;
+    RawPtrWillBeMember<HTMLMediaElement> m_element;
 
     Mode m_mode;