Fix virtual/override/final usage in Source/modules/.

Source/modules/mediasource/SourceBufferList.h

Index: Source/modules/mediasource/SourceBufferList.h
diff --git a/Source/modules/mediasource/SourceBufferList.h b/Source/modules/mediasource/SourceBufferList.h
index f3661e222bdabf3ffa79c3d148f625617f81dfcc..44685e3d76a4519b4b79a1ad2b0ecfe1e0c49f65 100644
--- a/Source/modules/mediasource/SourceBufferList.h
+++ b/Source/modules/mediasource/SourceBufferList.h
@@ -47,7 +47,7 @@ public:
     {
         return new SourceBufferList(context, asyncEventQueue);
     }
-    virtual ~SourceBufferList();
+    ~SourceBufferList() override;
 
     unsigned length() const { return m_list.size(); }
     SourceBuffer* item(unsigned index) const { return (index < m_list.size()) ? m_list[index].get() : 0; }
@@ -60,8 +60,8 @@ public:
     void clear();
 
     // EventTarget interface
-    virtual const AtomicString& interfaceName() const override;
-    virtual ExecutionContext* executionContext() const override;
+    const AtomicString& interfaceName() const override;
+    ExecutionContext* executionContext() const override;
 
     DECLARE_VIRTUAL_TRACE();