[wip] test branch in win native theme

ui/native_theme/native_theme_win.cc

Index: ui/native_theme/native_theme_win.cc
diff --git a/ui/native_theme/native_theme_win.cc b/ui/native_theme/native_theme_win.cc
index e1db2cc36ca4226abc5fe3d3f18428fd610b749a..12dabe04018745091cc026d275ce5d69379b7a81 100644
--- a/ui/native_theme/native_theme_win.cc
+++ b/ui/native_theme/native_theme_win.cc
@@ -280,6 +280,7 @@ void NativeThemeWin::Paint(cc::PaintCanvas* canvas,
   }
 
   HDC surface = skia::GetNativeDrawingContext(canvas);
+  CHECK(!surface);
 
   // When drawing the task manager or the bookmark editor, we draw into an
   // offscreen buffer, where we can use OS-specific drawing routines for