Bug 1673000 [Linux] Use Gtk color picker, r=jhorak

Differential Revision: https://phabricator.services.mozilla.com/D120324

widget/gtk/nsColorPicker.cpp

@@ -94,7 +94,7 @@ NS_IMETHODIMP nsColorPicker::Open(
       GTK_WINDOW(mParentWidget->GetNativeData(NS_NATIVE_SHELLWIDGET));
 
 #if defined(ACTIVATE_GTK3_COLOR_PICKER)
-  GtkWidget* color_chooser = gtk_color_chooser_dialog_new(title, parent_window);
+  GtkWidget* color_chooser = gtk_color_chooser_dialog_new(title.get(), parent_window);
 
   if (parent_window) {
     GtkWindow* window = GTK_WINDOW(color_chooser);

widget/gtk/nsColorPicker.h

@@ -12,10 +12,8 @@
 #include "nsIColorPicker.h"
 #include "nsString.h"
 
-// Don't activate the GTK3 color picker for now, because it is missing a few
-// things, mainly the ability to let the user select a color on the screen.
-// See bug 1198256.
-#undef ACTIVATE_GTK3_COLOR_PICKER
+// Enable Gtk3 system color picker.
+#define ACTIVATE_GTK3_COLOR_PICKER 1
 
 class nsIWidget;