Don't rely on order of Bind to EVT_TRACK_PANEL_TIMER from project...

... instead, re-process the event, and let each handler bind to the one it
depends on.

This still leaves a critical ordering of construction of playback scroller and
play indicator overlay in AudacityProject::AudacityProject (reverse of the
previous), but that will be removed by other means.

src/Project.cpp

@@ -1178,8 +1178,6 @@ AudacityProject::AudacityProject(wxWindow * parent, wxWindowID id,
                                              mRuler);
    mTrackPanel->UpdatePrefs();
 
-   mIndicatorOverlay = std::make_unique<PlayIndicatorOverlay>(this);
-
    mCursorOverlay = std::make_unique<EditCursorOverlay>(this);
 
    mBackgroundCell = std::make_shared<BackgroundCell>(this);
@@ -1189,16 +1187,10 @@ AudacityProject::AudacityProject(wxWindow * parent, wxWindowID id,
    mScrubber = std::make_unique<Scrubber>(this);
 #endif
 
-   // More order dependencies here...
-   // This must follow construction of *mIndicatorOverlay, because it must
-   // attach its timer event handler later (so that its handler is invoked
-   // earlier)
    mPlaybackScroller = std::make_unique<PlaybackScroller>(this);
 
-   // This must follow construction of *mPlaybackScroller,
-   // because it must
-   // attach its timer event handler later (so that its handler is invoked
-   // earlier)
+   mIndicatorOverlay = std::make_unique<PlayIndicatorOverlay>(this);
+   
    this->Bind(EVT_TRACK_PANEL_TIMER,
       &ViewInfo::OnTimer,
       &mViewInfo);
@@ -5532,9 +5524,9 @@ int AudacityProject::GetEstimatedRecordingMinsLeftOnDisk(long lCaptureChannels)
 AudacityProject::PlaybackScroller::PlaybackScroller(AudacityProject *project)
 : mProject(project)
 {
-   mProject->Bind(EVT_TRACK_PANEL_TIMER,
-                     &PlaybackScroller::OnTimer,
-                     this);
+   mProject->GetViewInfo().Bind(EVT_TRACK_PANEL_TIMER,
+      &PlaybackScroller::OnTimer,
+      this);
 }
 
 void AudacityProject::PlaybackScroller::OnTimer(wxCommandEvent &event)
@@ -5542,6 +5534,11 @@ void AudacityProject::PlaybackScroller::OnTimer(wxCommandEvent &event)
    // Let other listeners get the notification
    event.Skip();
 
+   auto cleanup = finally([&]{
+      // Propagate the message to other listeners bound to this
+      this->ProcessEvent( event );
+   });
+
    if(!mProject->IsAudioActive())
       return;
    else if (mMode == Mode::Refresh) {

src/ViewInfo.cpp

@@ -204,4 +204,6 @@ void ViewInfo::OnTimer(wxCommandEvent &event)
 {
    mRecentStreamTime = gAudioIO->GetStreamTime();
    event.Skip();
+   // Propagate the message to other listeners bound to this
+   this->ProcessEvent( event );
 }

src/tracks/ui/PlayIndicatorOverlay.cpp

@@ -110,9 +110,9 @@ void PlayIndicatorOverlayBase::Draw(OverlayPanel &panel, wxDC &dc)
 PlayIndicatorOverlay::PlayIndicatorOverlay(AudacityProject *project)
 : PlayIndicatorOverlayBase(project, true)
 {
-   mProject->Bind(EVT_TRACK_PANEL_TIMER,
-                     &PlayIndicatorOverlay::OnTimer,
-                     this);
+   mProject->GetPlaybackScroller().Bind(EVT_TRACK_PANEL_TIMER,
+      &PlayIndicatorOverlay::OnTimer,
+      this);
 }
 
 PlayIndicatorOverlay::~PlayIndicatorOverlay()