MacViewsBrowser: Fix omnibox crash due to failed DCHECK.

ui/views/controls/textfield/textfield.h

Index: ui/views/controls/textfield/textfield.h
diff --git a/ui/views/controls/textfield/textfield.h b/ui/views/controls/textfield/textfield.h
index 54391a380cb8ac1b51e0dd753f01014f045b569b..706e3333a44c747678b909d6b2a75f2af09fac56 100644
--- a/ui/views/controls/textfield/textfield.h
+++ b/ui/views/controls/textfield/textfield.h
@@ -212,8 +212,6 @@ class VIEWS_EXPORT Textfield : public View,
   bool OnMousePressed(const ui::MouseEvent& event) override;
   bool OnMouseDragged(const ui::MouseEvent& event) override;
   void OnMouseReleased(const ui::MouseEvent& event) override;
-  bool OnKeyPressed(const ui::KeyEvent& event) override;
-  bool OnKeyReleased(const ui::KeyEvent& event) override;
   void OnGestureEvent(ui::GestureEvent* event) override;
   bool AcceleratorPressed(const ui::Accelerator& accelerator) override;
   bool CanHandleAccelerators() const override;
@@ -323,6 +321,13 @@ class VIEWS_EXPORT Textfield : public View,
  private:
   friend class TextfieldTestApi;
 
+  // View overrides:
+  // Declared final since overriding by subclasses would interfere with the
+  // accounting related to the scheduled text edit command. Subclasses should
+  // use TextfieldController::HandleKeyEvent, to intercept the key event.
+  bool OnKeyPressed(const ui::KeyEvent& event) final;
+  bool OnKeyReleased(const ui::KeyEvent& event) final;
+
   // Handles a request to change the value of this text field from software
   // using an accessibility API (typically automation software, screen readers
   // don't normally use this). Sets the value and clears the selection.