GTK: Use GTK+ theme selection colors and plumb them into webkit.

webkit/tools/test_shell/layout_test_controller.h

Index: webkit/tools/test_shell/layout_test_controller.h
diff --git a/webkit/tools/test_shell/layout_test_controller.h b/webkit/tools/test_shell/layout_test_controller.h
index 398a8e68e5220f6a34afdae32c73098f219dcd2e..9015e4772ac5351b62afb6b07afb6b562d41edeb 100644
--- a/webkit/tools/test_shell/layout_test_controller.h
+++ b/webkit/tools/test_shell/layout_test_controller.h
@@ -217,6 +217,10 @@ class LayoutTestController : public CppBoundClass {
   // Allows layout tests to exec scripts at WebInspector side.
   void evaluateInWebInspector(const CppArgumentList& args, CppVariant* result);
 
+  // Forces the selection colors for testing under Linux.
+  void forceRedSelectionColors(const CppArgumentList& args,
+                               CppVariant* result);
+
  public:
   // The following methods are not exposed to JavaScript.
   void SetWorkQueueFrozen(bool frozen) { work_queue_.set_frozen(frozen); }