WIP - mask a view's layer by its view coordinates

ui/views/controls/button/md_text_button.h

 // Copyright 2015 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 UI_VIEWS_CONTROLS_BUTTON_MD_TEXT_BUTTON_H_
 #define UI_VIEWS_CONTROLS_BUTTON_MD_TEXT_BUTTON_H_
 
 #include <memory>
 
 #include "base/optional.h"
@@ skipping 18 matching lines @@
   // See |is_prominent_|.
   void SetProminent(bool is_prominent);
 
   // See |bg_color_override_|.
   void SetBgColorOverride(const base::Optional<SkColor>& color);
 
   // View:
   void OnPaintBackground(gfx::Canvas* canvas) override;
 
   // LabelButton:
+/*
+void OnPaint(gfx::Canvas* canvas) override;
+void PaintChildren(const ui::PaintContext& context);
+*/
+  bool GetNeedsNotificationWhenVisibleBoundsChange() const override;
+  void OnVisibleBoundsChanged() override;
+  void OnLayerBoundsChanged(const gfx::Rect& old_bounds) override;
   void OnFocus() override;
   void OnBlur() override;
   void OnNativeThemeChanged(const ui::NativeTheme* theme) override;
   std::unique_ptr<InkDrop> CreateInkDrop() override;
   std::unique_ptr<views::InkDropRipple> CreateInkDropRipple() const override;
   std::unique_ptr<views::InkDropHighlight> CreateInkDropHighlight()
       const override;
   SkColor GetInkDropBaseColor() const override;
   void SetEnabledTextColors(SkColor color) override;
   void SetText(const base::string16& text) override;
   void AdjustFontSize(int size_delta) override;
   void UpdateStyleToIndicateDefaultStatus() override;
   void StateChanged() override;
 
  protected:
   // LabelButton:
   void SetFontList(const gfx::FontList& font_list) override;
 
  private:
   explicit MdTextButton(ButtonListener* listener);
 
   void UpdatePadding();
   void UpdateColors();
 
   // True if this button uses prominent styling (blue fill, etc.).
   bool is_prominent_;
 
+  gfx::Rect last_visible_bounds_;
+  std::unique_ptr<ui::LayerDelegate> mask_layer_delegate_;
+  ui::Layer mask_layer_;
+
   // When set, this provides the background color.
   base::Optional<SkColor> bg_color_override_;
 
   DISALLOW_COPY_AND_ASSIGN(MdTextButton);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_BUTTON_MD_TEXT_BUTTON_H_