Clear root window when the aura root window is moved/resized

ui/aura/root_window_host_linux.cc

Index: ui/aura/root_window_host_linux.cc
diff --git a/ui/aura/root_window_host_linux.cc b/ui/aura/root_window_host_linux.cc
index 1f8cc0d1431cf0e3bcd670b3ca9694ebfa67b05a..6eea168a47f49487b14eb26396a618e30070b466 100644
--- a/ui/aura/root_window_host_linux.cc
+++ b/ui/aura/root_window_host_linux.cc
@@ -511,6 +511,22 @@ bool RootWindowHostLinux::Dispatch(const base::NativeEvent& event) {
         delegate_->OnHostResized(bounds.size());
       if (origin_changed)
         delegate_->OnHostMoved(bounds_.origin());
+#if defined(OS_CHROMEOS)
+      // TODO(oshima): Clear the root when the window is moved or
+      // resized while the extended desktop is disabled.
+      // crbug.com/152003.
+      if (base::chromeos::IsRunningOnChromeOS()) {
+        XGCValues gc_values = {0};
+        gc_values.foreground = BlackPixel(xdisplay_, DefaultScreen(xdisplay_));
+        GC gc = XCreateGC(xdisplay_, x_root_window_, GCForeground, &gc_values);
+        XFillRectangle(xdisplay_, x_root_window_, gc,
+                       x_root_bounds_.x(),
+                       x_root_bounds_.y(),
+                       x_root_bounds_.width(),
+                       x_root_bounds_.height());
+        XFreeGC(xdisplay_, gc);
+      }
+#endif
       break;
     }
     case GenericEvent: