Linux: move X operations from the IO to UI2 thread.

webkit/tools/test_shell/test_shell_x11.h

+#ifndef WEBKIT_TOOLS_TEST_SHELL_TEST_SHELL_X11_H
+#define WEBKIT_TOOLS_TEST_SHELL_TEST_SHELL_X11_H
+
+// This header is required because one cannot include both Xlib headers and
+// WebKit headers in the same source file.
+
+typedef struct _XDisplay Display;
+
+namespace test_shell_x11 {
+
+// Return an Xlib Display pointer for the given widget
+Display* GtkWidgetGetDisplay(GtkWidget* widget);
+// Return the screen number for the given widget
+int GtkWidgetGetScreenNum(GtkWidget* widget);
+
+}  // namespace test_shell_x11
+
+#endif  // !WEBKIT_TOOLS_TEST_SHELL_TEST_SHELL_X11_H