Dont composite if rgba is not supported.

views/widget/widget_gtk.cc

Index: views/widget/widget_gtk.cc
diff --git a/views/widget/widget_gtk.cc b/views/widget/widget_gtk.cc
index badafecb3f6b071ee51c94c7826f59b36db63e5c..5dea13c51aae3631e8cb2e30fcddf85693ffe758 100644
--- a/views/widget/widget_gtk.cc
+++ b/views/widget/widget_gtk.cc
@@ -962,7 +962,8 @@ gboolean WidgetGtk::OnPaint(GtkWidget* widget, GdkEventExpose* event) {
   if (transparent_ && type_ == TYPE_CHILD) {
     // Clear the background before drawing any view and native components.
     DrawTransparentBackground(widget, event);
-    if (!CompositePainter::IsComposited(widget_)) {
+    if (!CompositePainter::IsComposited(widget_) &&
+        gdk_screen_is_composited(gdk_screen_get_default())) {
       // Let the parent draw the content only after something is drawn on
       // the widget.
       CompositePainter::SetComposited(widget_);