Overlay scrollbars flush with window edge

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 184 matching lines @@
   };
 
   enum ScrollbarOverlayColorTheme {
     ScrollbarOverlayColorThemeDark,
     ScrollbarOverlayColorThemeLight
   };
 
   struct ScrollbarThumbExtraParams {
     bool is_hovering;
     ScrollbarOverlayColorTheme scrollbar_theme;
+    bool isLeftVerticalScrollbar;

[Evan Stade, 2017/03/28 00:01:56]

nit: is_left_vertical_scrollbar

but also, it seems like we should instead be splitting the part into two (one
for left vertical bar and one for right vertical bar), or making this param a
generic rtl parameter.

[chaopeng, 2017/03/28 02:58:40]

Sorry, I don't get this one. Why we need is right vertical scrollbar? We use
IsLeftSideVerticalScrollbar everywhere like this.
https://cs.chromium.org/chromium/src/cc/input/scrollbar.h?q=scrollba&l=26

[Evan Stade, 2017/03/28 03:14:36]

I meant that the Part enum should have different values.

   };
 
   struct SliderExtraParams {
     bool vertical;
     bool in_drag;
   };
 
   struct TextFieldExtraParams {
     bool is_text_area;
     bool is_listbox;
@@ skipping 216 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_