ui: Remove a bunch of uses of gfx::Canvas::ExtractImageRep()

ash/common/frame/caption_buttons/frame_caption_button.h

 // Copyright 2013 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 ASH_COMMON_FRAME_CAPTION_BUTTONS_FRAME_CAPTION_BUTTON_H_
 #define ASH_COMMON_FRAME_CAPTION_BUTTONS_FRAME_CAPTION_BUTTON_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
@@ skipping 48 matching lines @@
 
   CaptionButtonIcon icon() const { return icon_; }
 
   void set_size(const gfx::Size& size) { size_ = size; }
 
  protected:
   // views::CustomButton override:
   void OnGestureEvent(ui::GestureEvent* event) override;
 
  private:
-  // Paints |to_center| centered within the button with |alpha|.
-  void PaintCentered(gfx::Canvas* canvas,
-                     const gfx::ImageSkia& to_center,
-                     int alpha);
+  // Determines what alpha to use for the icon based on animation and
+  // active state.
+  int GetAlphaForIcon(int base_alpha) const;
 
   // The button's current icon.
   CaptionButtonIcon icon_;
 
   // The size of the button.
   gfx::Size size_;
 
   // Whether the button should be painted as active.
   bool paint_as_active_;
 
@@ skipping 14 matching lines @@
   // Crossfade animation started when the button's images are changed by
   // SetImage().
   std::unique_ptr<gfx::SlideAnimation> swap_images_animation_;
 
   DISALLOW_COPY_AND_ASSIGN(FrameCaptionButton);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_FRAME_CAPTION_BUTTONS_FRAME_CAPTION_BUTTON_H_