ash: Clean up system background layer.

ui/aura/root_window_host_win.cc

Index: ui/aura/root_window_host_win.cc
diff --git a/ui/aura/root_window_host_win.cc b/ui/aura/root_window_host_win.cc
index fbe54971b4a5441f58dc53922f9fcee33462d14f..f21170c10546c1d9b161358df80e5b9a1d3de889 100644
--- a/ui/aura/root_window_host_win.cc
+++ b/ui/aura/root_window_host_win.cc
@@ -178,6 +178,13 @@ bool RootWindowHostWin::ConfineCursorToRootWindow() {
   return ClipCursor(&window_rect) != 0;
 }
 
+bool RootWindowHostWin::CopyAreaToSkCanvas(const gfx::Rect& source_bounds,
+                                           const gfx::Point& dest_offset,
+                                           SkCanvas* canvas) {
+  NOTIMPLEMENTED();
+  return false;
+}
+
 bool RootWindowHostWin::GrabSnapshot(
     const gfx::Rect& snapshot_bounds,
     std::vector<unsigned char>* png_representation) {