MixerBoard no longer needs update at undo push...

... it does that sooner, and ony when needed, when relevant track data really
change, by listening to the TrackList.

src/Project.cpp

@@ -4592,7 +4592,6 @@ void AudacityProject::InitialState()
    GetMenuManager(*this).ModifyUndoMenuItems(*this);
 
    GetMenuManager(*this).UpdateMenus(*this);
-   this->UpdateMixerBoard();
 }
 
 bool AudacityProject::UndoAvailable()
@@ -4627,14 +4626,6 @@ void AudacityProject::PushState(const wxString &desc,
 
    GetMenuManager(*this).UpdateMenus(*this);
 
-   // Some state pushes, like changing a track gain control (& probably others),
-   // should not repopulate MixerBoard.
-   // Others, such as deleting adding a wave track, obviously do.
-   // Could categorize these state changes, but for now...
-   // It's crucial to not do that repopulating during playback.
-   if (!gAudioIO->IsStreamActive(GetAudioIOToken()))
-      this->UpdateMixerBoard();
-
    if (GetTracksFitVerticallyZoomed())
       ViewActions::DoZoomFitV(*this);
    if((flags & UndoPush::AUTOSAVE) != UndoPush::MINIMAL)
@@ -4722,18 +4713,6 @@ void AudacityProject::SetStateTo(unsigned int n)
    GetMenuManager(*this).ModifyUndoMenuItems(*this);
 }
 
-void AudacityProject::UpdateMixerBoard()
-{
-   if (!mMixerBoard)
-      return;
-   mMixerBoard->UpdateTrackClusters();
-
-   // Vaughan, 2011-01-28: AudacityProject::UpdateMixerBoard() is called on state changes,
-   //   so don't really need to call UpdateMeters().
-   //mMixerBoard->UpdateMeters(gAudioIO->GetStreamTime(), (mLastPlayMode == loopedPlay));
-}
-
-
 void AudacityProject::RecreateMixerBoard( )
 {
    wxASSERT( mMixerBoard );

src/Project.h

@@ -605,8 +605,6 @@ public:
 
    void PopState(const UndoState &state);
 
-   void UpdateMixerBoard();
-
    void GetRegionsByLabel( Regions &regions );
 
    void AutoSave();