sound: Add tooltips to all speaker test buttons

With this change, Orca now reads the word
"speaker", for example: "Front Left Speaker push button"
instead of "Front Left push button".

Also, remove the a11y labels because Orca also reads
tooltips.

panels/sound/cc-speaker-test-button.c

@@ -207,15 +207,16 @@ cc_speaker_test_button_new (GSoundContext         *context,
                             pa_channel_position_t  position)
 {
   CcSpeakerTestButton *self = g_object_new (CC_TYPE_SPEAKER_TEST_BUTTON, NULL);
+  g_autofree gchar *tooltip_text = NULL;
 
   self->context = g_object_ref (context);
   self->position = position;
   update_icon (self);
-  gtk_accessible_update_property (GTK_ACCESSIBLE (self),
-                                  GTK_ACCESSIBLE_PROPERTY_LABEL,
-                                  pa_channel_position_to_pretty_string (position),
-                                  -1);
 
+  /* Translators: This is the tooltip for a speaker test button, %s is an already translated
+     speaker position, like "Front Left" or "Rear Center". */
+  tooltip_text = g_strdup_printf (_("%s Speaker"), pa_channel_position_to_pretty_string (position));
+  gtk_widget_set_tooltip_text (GTK_WIDGET (self), tooltip_text);
 
   return GTK_WIDGET (self);
 }

panels/sound/cc-speaker-test-button.h

@@ -20,6 +20,7 @@
 #include <gsound.h>
 #include <gtk/gtk.h>
 #include <pulse/pulseaudio.h>
+#include <glib/gi18n.h>
 
 G_BEGIN_DECLS
 

po/POTFILES.in

@@ -199,6 +199,7 @@ panels/sound/cc-fade-slider.ui
 panels/sound/cc-output-test-wheel.c
 panels/sound/cc-output-test-window.ui
 panels/sound/cc-sound-panel.ui
+panels/sound/cc-speaker-test-button.c
 panels/sound/cc-subwoofer-slider.ui
 panels/sound/cc-volume-levels-window.ui
 panels/sound/cc-volume-slider.c