Add a new GetSystemColor method to native theme.

ui/gfx/native_theme_win.cc

Index: ui/gfx/native_theme_win.cc
diff --git a/ui/gfx/native_theme_win.cc b/ui/gfx/native_theme_win.cc
index 9114e354b1a8d7b3e6933938da3abb8b675b44fd..b5751e14ad04d9528c863de503cab8558df9f580 100644
--- a/ui/gfx/native_theme_win.cc
+++ b/ui/gfx/native_theme_win.cc
@@ -55,6 +55,10 @@ void SetCheckerboardShader(SkPaint* paint, const RECT& align_rect) {
   SkSafeUnref(paint->setShader(shader));
 }
 
+SkColor WinColorToSkColor(COLORREF color) {
+  return SkColorSetRGB(GetRValue(color), GetGValue(color), GetBValue(color));
+}
+
 }  // namespace
 
 namespace gfx {
@@ -1682,4 +1686,17 @@ int NativeThemeWin::GetWindowsState(Part part,
   return state_id;
 }
 
+SkColor NativeThemeWin::GetSystemColor(ColorId color_id) const {
+  switch (color_id) {
+    case kDialogBackgroundColor:
+      // TODO(benrg): Should this use the new Windows theme functions? The old
+      // code in DialogClientView::OnPaint used GetSysColor(COLOR_3DFACE).
+      return WinColorToSkColor(GetSysColor(COLOR_3DFACE));
+    default:
+      NOTREACHED() << "Invalid color_id: " << color_id;
+      break;
+  }
+  return SkColorSetRGB(255, 0, 0);  // warning red
+}
+
 }  // namespace gfx