Native themes: Add menu separator part

ui/native_theme/native_theme_base.cc

Index: ui/native_theme/native_theme_base.cc
diff --git a/ui/native_theme/native_theme_base.cc b/ui/native_theme/native_theme_base.cc
index ddf2128cbd446991458e4fe61cf35b84b6de1161..a545f0e80df4383593d9e444609d68c4118ec937 100644
--- a/ui/native_theme/native_theme_base.cc
+++ b/ui/native_theme/native_theme_base.cc
@@ -184,6 +184,9 @@ void NativeThemeBase::Paint(SkCanvas* canvas,
     case kMenuPopupBackground:
       PaintMenuPopupBackground(canvas, rect.size(), extra.menu_background);
       break;
+    case kMenuPopupSeparator:
+      PaintMenuSeparator(canvas, state, rect, extra.menu_separator);
+      break;
     case kMenuItemBackground:
       PaintMenuItemBackground(canvas, state, rect, extra.menu_item);
       break;
@@ -774,6 +777,16 @@ void NativeThemeBase::PaintMenuItemBackground(
   // By default don't draw anything over the normal background.
 }
 
+void NativeThemeBase::PaintMenuSeparator(
+    SkCanvas* canvas,
+    State state,
+    const gfx::Rect& rect,
+    const MenuSeparatorExtraParams& menu_separator) const {

[sky, 2017/01/25 21:57:22]

Why is there rect and menu_separator.paint_rect? AFAICT you never use rect.
Seems better to use rect as an arg.

[Tom (Use chromium acct), 2017/01/25 22:25:44]

rect is the region the paint context is clipped to.  paint_rect is contained in
rect, and is used as a suggestion for where to paint the separator.

rect is used in NativeThemeGtk3, where menu_separator.paint_rect is not.  The
reason for this is Chrome usually wants to render a 1px border, but Gtk borders
might have a minimum size of 2px (eg. when borders are two-tone).

+  SkPaint paint;
+  paint.setColor(GetSystemColor(ui::NativeTheme::kColorId_MenuSeparatorColor));
+  canvas->drawRect(gfx::RectToSkRect(*menu_separator.paint_rect), paint);
+}
+
 void NativeThemeBase::PaintSliderTrack(SkCanvas* canvas,
                                        State state,
                                        const gfx::Rect& rect,