Standardize usage of virtual/override/final specifiers.

ash/accelerators/magnifier_key_scroller.h

Index: ash/accelerators/magnifier_key_scroller.h
diff --git a/ash/accelerators/magnifier_key_scroller.h b/ash/accelerators/magnifier_key_scroller.h
index 1ef78fbdde3bbd7464d641cf3a8c5cdbde659a7f..2e16533791bbaa9b78e786603cea06859a539d3c 100644
--- a/ash/accelerators/magnifier_key_scroller.h
+++ b/ash/accelerators/magnifier_key_scroller.h
@@ -39,13 +39,13 @@ class ASH_EXPORT MagnifierKeyScroller : public KeyHoldDetector::Delegate {
 
  private:
   // KeyHoldDetector overrides:
-  virtual bool ShouldProcessEvent(const ui::KeyEvent* event) const override;
-  virtual bool IsStartEvent(const ui::KeyEvent* event) const override;
-  virtual void OnKeyHold(const ui::KeyEvent* event) override;
-  virtual void OnKeyUnhold(const ui::KeyEvent* event) override;
+  bool ShouldProcessEvent(const ui::KeyEvent* event) const override;
+  bool IsStartEvent(const ui::KeyEvent* event) const override;
+  void OnKeyHold(const ui::KeyEvent* event) override;
+  void OnKeyUnhold(const ui::KeyEvent* event) override;
 
   MagnifierKeyScroller();
-  virtual ~MagnifierKeyScroller();
+  ~MagnifierKeyScroller() override;
 
   DISALLOW_COPY_AND_ASSIGN(MagnifierKeyScroller);
 };