MediaStreamSource: verify unlocked state when finalizing.

third_party/WebKit/Source/platform/mediastream/MediaStreamSource.h

Index: third_party/WebKit/Source/platform/mediastream/MediaStreamSource.h
diff --git a/third_party/WebKit/Source/platform/mediastream/MediaStreamSource.h b/third_party/WebKit/Source/platform/mediastream/MediaStreamSource.h
index 8b7586051e17e0f42ad99b89aa698371dab52943..010dfbe135db0ad5243606708a619d50050bee0a 100644
--- a/third_party/WebKit/Source/platform/mediastream/MediaStreamSource.h
+++ b/third_party/WebKit/Source/platform/mediastream/MediaStreamSource.h
@@ -75,6 +75,8 @@ class PLATFORM_EXPORT MediaStreamSource final
                                    ReadyState = ReadyStateLive,
                                    bool requiresConsumer = false);
 
+  ~MediaStreamSource();
+
   const String& id() const { return m_id; }
   StreamType type() const { return m_type; }
   const String& name() const { return m_name; }