Ensure that the focus ring in the bookmarks bar does not paint outside the parent view.

ui/views/controls/scroll_view.h

Index: ui/views/controls/scroll_view.h
diff --git a/ui/views/controls/scroll_view.h b/ui/views/controls/scroll_view.h
index af9111a05cae1a2dd25daba64afe629560c7751e..62d9d32ba8d93c2d98fee5474ab8f34c5b2cc494 100644
--- a/ui/views/controls/scroll_view.h
+++ b/ui/views/controls/scroll_view.h
@@ -105,6 +105,7 @@ class VIEWS_EXPORT ScrollView : public View, public ScrollBarController {
   void OnGestureEvent(ui::GestureEvent* event) override;
   const char* GetClassName() const override;
   void OnNativeThemeChanged(const ui::NativeTheme* theme) override;
+  void OnChildLayerChanged(View* child) override;
 
   // ScrollBarController overrides:
   void ScrollToPosition(ScrollBar* source, int position) override;
@@ -204,6 +205,9 @@ class VIEWS_EXPORT ScrollView : public View, public ScrollBarController {
   // Focus ring, if one is installed.
   View* focus_ring_ = nullptr;
 
+  // Set to true if we enabled layering for the viewport.
+  bool viewport_layer_enabled_ = false;
+
   DISALLOW_COPY_AND_ASSIGN(ScrollView);
 };