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..9a3b1b6cf71e5f6ca8b9753edb778d465ef62cee 100644
--- a/ui/views/controls/textfield/textfield.h
+++ b/ui/views/controls/textfield/textfield.h
@@ -212,8 +212,15 @@ 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;
+
+  // OnKey[Pressed/Released] are virtual only so that they can be overridden in
+  // tests. Subclasses should not extend these, since it would interfere with
+  // the accounting related to the scheduled text edit command. Instead
+  // subclasses should use TextfieldController::HandleKeyEvent, to intercept the
+  // key event.
   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;