Draw omnibox shadow with a ninebox layer.

chrome/browser/ui/views/omnibox/omnibox_popup_contents_view.h

Index: chrome/browser/ui/views/omnibox/omnibox_popup_contents_view.h
diff --git a/chrome/browser/ui/views/omnibox/omnibox_popup_contents_view.h b/chrome/browser/ui/views/omnibox/omnibox_popup_contents_view.h
index ccf42a35ef8977e8dbd8d488f7148f291f888d2e..7955ef25e1579d2648b3cb2a75d96a2ee7a2f61c 100644
--- a/chrome/browser/ui/views/omnibox/omnibox_popup_contents_view.h
+++ b/chrome/browser/ui/views/omnibox/omnibox_popup_contents_view.h
@@ -58,6 +58,7 @@ class OmniboxPopupContentsView : public views::View,
   // views::View:
   void Layout() override;
   views::View* GetTooltipHandlerForPoint(const gfx::Point& point) override;
+  void OnBoundsChanged(const gfx::Rect& previous_bounds) override;
   bool OnMousePressed(const ui::MouseEvent& event) override;
   bool OnMouseDragged(const ui::MouseEvent& event) override;
   void OnMouseReleased(const ui::MouseEvent& event) override;
@@ -66,7 +67,9 @@ class OmniboxPopupContentsView : public views::View,
   void OnMouseEntered(const ui::MouseEvent& event) override;
   void OnMouseExited(const ui::MouseEvent& event) override;
   void OnGestureEvent(ui::GestureEvent* event) override;
-
+  void ViewHierarchyChanged(
+      const ViewHierarchyChangedDetails& details) override;
+bool experiment_started_ = false;
   bool IsSelectedIndex(size_t index) const;
   bool IsHoveredIndex(size_t index) const;
   gfx::Image GetIconIfExtensionMatch(size_t index) const;
@@ -93,7 +96,6 @@ class OmniboxPopupContentsView : public views::View,
 
   // views::View:
   const char* GetClassName() const override;
-  void OnPaint(gfx::Canvas* canvas) override;
   void PaintChildren(const ui::PaintContext& context) override;
 
   // views::ViewTargeterDelegate:
@@ -141,6 +143,9 @@ class OmniboxPopupContentsView : public views::View,
   // The font list used for result rows, based on the omnibox font list.
   gfx::FontList font_list_;
 
+  // The ninebox layer that draws a drop shadow above and below the popup.
+  std::unique_ptr<ui::Layer> shadow_layer_;
+
   // If the user cancels a dragging action (i.e. by pressing ESC), we don't have
   // a convenient way to release mouse capture. Instead we use this flag to
   // simply ignore all remaining drag events, and the eventual mouse release