Fix frame-rate display using times from previous playback

The average times weren't reset so the last draw time would be used
making the FPS seem low for the first ~10 or so frames.
The averages from the last time the playback operator ran were also
used which could be misleading although this was also limited to the
first 8 frames.

Resolve by freeing the ScreenFrameRateInfo on animation start/end.

source/blender/editors/include/ED_screen.hh

@@ -453,6 +453,11 @@ void ED_scene_fps_average_accumulate(struct Scene *scene, const double ltime);
  * \return True when #ScreenFrameRateInfo::fps_average should be used.
  */
 bool ED_scene_fps_average_calc(const struct Scene *scene);
+/**
+ * Clear run-time data for accumulating animation playback average times.
+ */
+void ED_scene_fps_average_clear(Scene *scene);
+
 /**
  * Toggle operator.
  */

source/blender/editors/screen/screen_edit.cc

@@ -1679,11 +1679,16 @@ ScrArea *ED_screen_temp_space_open(bContext *C,
   return area;
 }
 
+void ED_scene_fps_average_clear(Scene *scene)
+{
+  MEM_SAFE_FREE(scene->fps_info);
+}
+
 void ED_scene_fps_average_accumulate(Scene *scene, const double ltime)
 {
   if ((U.uiflag & USER_SHOW_FPS) == 0) {
     /* Playback stopped or shouldn't be running. */
-    MEM_SAFE_FREE(scene->fps_info);
+    ED_scene_fps_average_clear(scene);
     return;
   }
 
@@ -1744,6 +1749,7 @@ bool ED_scene_fps_average_calc(const Scene *scene)
       tot++;
     }
   }
+  printf("TOTAL WAS: %d\n", tot);
   if (tot) {
     fpsi->redrawtime_index = (fpsi->redrawtime_index + 1) % REDRAW_FRAME_AVERAGE;
     fps = fps / tot;

source/blender/editors/screen/screen_ops.cc

@@ -4942,6 +4942,7 @@ int ED_screen_animation_play(bContext *C, int sync, int mode)
   if (ED_screen_animation_playing(CTX_wm_manager(C))) {
     /* stop playback now */
     ED_screen_animation_timer(C, 0, 0, 0);
+    ED_scene_fps_average_clear(scene);
     BKE_sound_stop_scene(scene_eval);
 
     BKE_callback_exec_id_depsgraph(
@@ -4963,6 +4964,7 @@ int ED_screen_animation_play(bContext *C, int sync, int mode)
     }
 
     ED_screen_animation_timer(C, screen->redraws_flag, sync, mode);
+    ED_scene_fps_average_clear(scene);
 
     if (screen->animtimer) {
       wmTimer *wt = screen->animtimer;