Fix virtual/override/final usage in Source/core/dom/.

Source/core/dom/custom/CustomElementMicrotaskImportStep.h

Index: Source/core/dom/custom/CustomElementMicrotaskImportStep.h
diff --git a/Source/core/dom/custom/CustomElementMicrotaskImportStep.h b/Source/core/dom/custom/CustomElementMicrotaskImportStep.h
index 0509391a12be77196a47b531abb2fac05ec8713e..a7161e5f27d40f5f95a1abd45c5c16f00006f7af 100644
--- a/Source/core/dom/custom/CustomElementMicrotaskImportStep.h
+++ b/Source/core/dom/custom/CustomElementMicrotaskImportStep.h
@@ -54,7 +54,7 @@ class CustomElementMicrotaskImportStep : public CustomElementMicrotaskStep {
     WTF_MAKE_NONCOPYABLE(CustomElementMicrotaskImportStep);
 public:
     static PassOwnPtrWillBeRawPtr<CustomElementMicrotaskImportStep> create(HTMLImportChild*);
-    virtual ~CustomElementMicrotaskImportStep();
+    ~CustomElementMicrotaskImportStep() override;
 
     // API for HTML Imports
     void invalidate();
@@ -72,10 +72,10 @@ private:
     bool shouldWaitForImport() const;
 
     // CustomElementMicrotaskStep
-    virtual Result process() override final;
+    Result process() final;
 
 #if !defined(NDEBUG)
-    virtual void show(unsigned indent) override;
+    void show(unsigned indent) override;
 #endif
     WeakPtrWillBeWeakMember<HTMLImportChild> m_import;
 #if !ENABLE(OILPAN)