ash: Clean up system background layer.

ui/views/widget/desktop_root_window_host_linux.cc

Index: ui/views/widget/desktop_root_window_host_linux.cc
diff --git a/ui/views/widget/desktop_root_window_host_linux.cc b/ui/views/widget/desktop_root_window_host_linux.cc
index c135f6a3e9b580c04cb3c6e6c9a7570b2162a793..6dadcd07b5243a86afd2237d69ee329005df2f83 100644
--- a/ui/views/widget/desktop_root_window_host_linux.cc
+++ b/ui/views/widget/desktop_root_window_host_linux.cc
@@ -764,6 +764,14 @@ void DesktopRootWindowHostLinux::SetFocusWhenShown(bool focus_when_shown) {
   }
 }
 
+bool DesktopRootWindowHostLinux::CopyAreaToSkCanvas(
+    const gfx::Rect& source_bounds,
+    const gfx::Point& dest_offset,
+    SkCanvas* canvas) {
+  NOTIMPLEMENTED();
+  return false;
+}
+
 bool DesktopRootWindowHostLinux::GrabSnapshot(
       const gfx::Rect& snapshot_bounds,
       std::vector<unsigned char>* png_representation) {