Updated DropdownBarHost to use Layer clipping instead of OnPaint() clipping.

chrome/browser/ui/views/dropdown_bar_view.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_UI_VIEWS_DROPDOWN_BAR_VIEW_H_
 #define CHROME_BROWSER_UI_VIEWS_DROPDOWN_BAR_VIEW_H_
 
 #include "chrome/browser/ui/views/dropdown_bar_host.h"
 #include "chrome/browser/ui/views/dropdown_bar_host_delegate.h"
 #include "ui/views/accessible_pane_view.h"
 
 namespace gfx {
 class Canvas;
 class ImageSkia;
 }  // namespace gfx
 
 ////////////////////////////////////////////////////////////////////////////////
 //
 // The DropdownBarView is an abstract view to draw the UI controls of the
 // DropdownBarHost.
 //
 ////////////////////////////////////////////////////////////////////////////////
 class DropdownBarView : public views::AccessiblePaneView,
                         public DropdownBarHostDelegate {
  public:
   explicit DropdownBarView(DropdownBarHost* host);
   ~DropdownBarView() override;
 
-  // Updates the view to let it know where the host is clipping the
-  // dropdown widget (while animating the opening or closing of the widget).
-  void SetAnimationOffset(int offset) override;
-
-  // Returns the offset used while animating.
-  int animation_offset() const { return animation_offset_; }
-
  protected:
-  // views::View:
-  void OnPaint(gfx::Canvas* canvas) override;
-
   // Returns the DropdownBarHost that manages this view.
   DropdownBarHost* host() const { return host_; }
 
   void SetBackground(const gfx::ImageSkia* left_alpha_mask,
                      const gfx::ImageSkia* right_alpha_mask);
   void SetBorderFromIds(int left_border_image_id,
                         int middle_border_image_id,
                         int right_border_image_id);
 
  private:
   // The dropdown bar host that controls this view.
   DropdownBarHost* host_;
 
-  // While animating, the host clips the widget and draws only the bottom
-  // part of it. The view needs to know the pixel offset at which we are drawing
-  // the widget so that we can draw the curved edges that attach to the toolbar
-  // in the right location.
-  int animation_offset_;
-
   DISALLOW_COPY_AND_ASSIGN(DropdownBarView);
 };
 #endif  // CHROME_BROWSER_UI_VIEWS_DROPDOWN_BAR_VIEW_H_