Remove unused _cogl_swap_buffers_notify

Recently _cogl_swap_buffers_notify was added (in 142b229c5c) so that
Cogl would be notified when Clutter performs a swap buffers request for
a given onscreen framebuffer. It was expected this would be required for
the recent cogl_read_pixel optimization that was implemented (ref
1bdb0e6e98) but in the end it wasn't used.

Since it wasn't used in the end this patch removes the API.

clutter/cogl/cogl/cogl-framebuffer-private.h

@@ -212,9 +212,6 @@ _cogl_framebuffer_flush_journal (CoglFramebuffer *framebuffer);
 void
 _cogl_framebuffer_flush_dependency_journals (CoglFramebuffer *framebuffer);
 
-void
-_cogl_framebuffer_swap_notify (CoglFramebuffer *framebuffer);
-
 gboolean
 _cogl_framebuffer_try_fast_read_pixel (CoglFramebuffer *framebuffer,
                                        int x,

clutter/cogl/cogl/cogl-framebuffer.c

@@ -457,11 +457,6 @@ _cogl_framebuffer_clear (CoglFramebuffer *framebuffer,
                              cogl_color_get_alpha_float (color));
 }
 
-void
-_cogl_framebuffer_swap_notify (CoglFramebuffer *framebuffer)
-{
-}
-
 int
 _cogl_framebuffer_get_width (CoglFramebuffer *framebuffer)
 {

clutter/cogl/cogl/cogl.c

@@ -1109,14 +1109,3 @@ _cogl_error_quark (void)
 {
   return g_quark_from_static_string ("cogl-error-quark");
 }
-
-/* Until Cogl becomes responsible for handling swap-buffer requests
- * this API is used by Clutter to notify us when it issues a
- * swap-buffer on our behalf. */
-void
-_cogl_swap_buffers_notify (void)
-{
-  _COGL_GET_CONTEXT (ctx, NO_RETVAL);
-
-  _cogl_framebuffer_swap_notify (_cogl_get_draw_buffer ());
-}

clutter/cogl/cogl/cogl.h

@@ -1280,9 +1280,6 @@ _cogl_driver_error_quark (void);
 void
 _cogl_onscreen_clutter_backend_set_size (int width, int height);
 
-void
-_cogl_swap_buffers_notify (void);
-
 CoglFramebuffer *
 _cogl_get_draw_buffer (void);
 

clutter/egl/clutter-stage-egl.c

@@ -413,7 +413,6 @@ clutter_stage_egl_redraw (ClutterStageWindow *stage_window)
       CLUTTER_TIMER_START (_clutter_uprof_context, swapbuffers_timer);
       eglSwapBuffers (backend_egl->edpy, egl_surface);
       CLUTTER_TIMER_STOP (_clutter_uprof_context, swapbuffers_timer);
-      _cogl_swap_buffers_notify ();
     }
 
   /* reset the redraw clipping for the next paint... */

clutter/fruity/clutter-backend-fruity.c

@@ -77,7 +77,6 @@ clutter_backend_egl_redraw (ClutterBackend *backend,
   cogl_flush ();
   eglWaitGL();
   eglSwapBuffers (backend_egl->edpy,  stage_egl->egl_surface);
-  _cogl_swap_buffers_notify ();
 }
 
 static ClutterActor *

clutter/glx/clutter-stage-glx.c

@@ -648,8 +648,6 @@ clutter_stage_glx_redraw (ClutterStageWindow *stage_window)
       CLUTTER_TIMER_START (_clutter_uprof_context, swapbuffers_timer);
       glXSwapBuffers (backend_x11->xdpy, drawable);
       CLUTTER_TIMER_STOP (_clutter_uprof_context, swapbuffers_timer);
-
-      _cogl_swap_buffers_notify ();
     }
 
   backend_glx->last_video_sync_count = video_sync_count;

clutter/osx/clutter-stage-osx.c

@@ -159,7 +159,6 @@ clutter_stage_osx_get_wrapper (ClutterStageWindow *stage_window);
   _clutter_stage_do_paint (CLUTTER_STAGE (self->stage_osx->wrapper), NULL);
   cogl_flush ();
   [[self openGLContext] flushBuffer];
-  _cogl_swap_buffers_notify ();
 }
 
 /* In order to receive key events */

clutter/wayland/clutter-stage-wayland.c

@@ -506,8 +506,6 @@ wayland_swap_buffers (ClutterStageWayland *stage_wayland)
   wl_display_frame_callback (backend_wayland->wayland_display,
 			     wayland_frame_callback,
 			     stage_wayland);
-
-  _cogl_swap_buffers_notify ();
 }
 
 static void

clutter/win32/clutter-stage-win32.c

@@ -528,10 +528,7 @@ clutter_stage_win32_redraw (ClutterStageWindow *stage_window)
   cogl_flush ();
 
   if (stage_win32->client_dc)
-    {
+    SwapBuffers (stage_win32->client_dc);
-      SwapBuffers (stage_win32->client_dc);
-      _cogl_swap_buffers_notify ();
-    }
 }
 
 static void