Bug 1977 - Simpler rule for 'Default sample rate' and 'Project rate'.

After discussion it was felt that only using 'Default sample rate' for new projects was better.

src/Project.cpp

@@ -1351,6 +1351,10 @@ void AudacityProject::UpdatePrefsVariables()
    gPrefs->Read(wxT("/GUI/TracksFitVerticallyZoomed"), &mTracksFitVerticallyZoomed, false);
    //   gPrefs->Read(wxT("/GUI/UpdateSpectrogram"), &mViewInfo.bUpdateSpectrogram, true);
 
+   // This code to change an empty projects rate is currently disabled, after discussion.
+   // The rule 'Default sample rate' only affects newly created projects was felt to 
+   // be simpler and better.
+#if 0
    // The DefaultProjectSample rate is the rate for new projects.
    // Do not change this project's rate, unless there are no tracks.
    if( GetTrackCount() == 0){
@@ -1361,6 +1365,8 @@ void AudacityProject::UpdatePrefsVariables()
          bar->SetRate( mRate );
       }
    }
+#endif
+
    mDefaultFormat = QualityPrefs::SampleFormatChoice();
 
    gPrefs->Read(wxT("/AudioIO/SeekShortPeriod"), &mSeekShort, 1.0);

src/toolbars/SelectionBar.cpp

@@ -117,7 +117,6 @@ SelectionBar::SelectionBar()
    // Refer to bug #462 for a scenario where the division-by-zero causes
    // Audacity to fail.
    // We expect mRate to be set from the project later.
-   // We could just use AudioIO::GetOptimalSupportedSampleRate() here.
    mRate = (double) gPrefs->Read(wxT("/SamplingRate/DefaultProjectSampleRate"),
       AudioIO::GetOptimalSupportedSampleRate());
 
@@ -344,11 +343,11 @@ void SelectionBar::Populate()
 void SelectionBar::UpdatePrefs()
 {
    // The project rate is no longer driven from here.
-   // IF /SamplingRate/DefaultProjectSampleRate has changed, that is sent to the project.
+   // When preferences change, the Project learns about it too.
-   // IF the project has no tracks, then the project updates its sample rate, and
+   // If necessary we can drive the SelectionBar mRate via the Project
-   // signals that back to the SelectionBar via SetRate().
+   // calling our SetRate().
-   // Usually though there are tracks, and changes to that pref will only affect new
+   // As of 13-Sep-2018, changes to the sample rate pref will only affect 
-   // or empty projects.
+   // creation of new projects, not the smaple rate in existing ones.
 
    wxCommandEvent e;
    e.SetInt(mStartTime->GetFormatIndex());