Aura overlay scrollbars adjust color for dark backgrounds

ui/native_theme/native_theme.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 UI_NATIVE_THEME_NATIVE_THEME_H_
 #define UI_NATIVE_THEME_NATIVE_THEME_H_
 
 #include "base/macros.h"
 #include "base/observer_list.h"
 #include "build/build_config.h"
@@ skipping 153 matching lines @@
 
   struct ScrollbarTrackExtraParams {
     bool is_upper;
     int track_x;
     int track_y;
     int track_width;
     int track_height;
     int classic_state;  // Used on Windows when uxtheme is not available.
   };
 
+  enum ScrollbarOverlayColorTheme {
+    ScrollbarOverlayColorThemeDark,
+    ScrollbarOverlayColorThemeLight
+  };
+
   struct ScrollbarThumbExtraParams {
     bool is_hovering;
+    ScrollbarOverlayColorTheme scrollbar_theme;
   };
 
   struct SliderExtraParams {
     bool vertical;
     bool in_drag;
   };
 
   struct TextFieldExtraParams {
     bool is_text_area;
     bool is_listbox;
@@ skipping 42 matching lines @@
                      const gfx::Rect& rect,
                      const ExtraParams& extra) const = 0;
 
   // Paint part during state transition, used for overlay scrollbar state
   // transition animation.
   virtual void PaintStateTransition(SkCanvas* canvas,
                                     Part part,
                                     State startState,
                                     State endState,
                                     double progress,
-                                    const gfx::Rect& rect) const { }
+                                    const gfx::Rect& rect,
+                                    ScrollbarOverlayColorTheme theme) const {}
 
   // Supports theme specific colors.
   void SetScrollbarColors(unsigned inactive_color,
                           unsigned active_color,
                           unsigned track_color);
 
   // Colors for GetSystemColor().
   enum ColorId {
     // Windows
     kColorId_WindowBackground,
@@ skipping 125 matching lines @@
  private:
   // Observers to notify when the native theme changes.
   base::ObserverList<NativeThemeObserver> native_theme_observers_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeTheme);
 };
 
 }  // namespace ui
 
 #endif  // UI_NATIVE_THEME_NATIVE_THEME_H_