Define and use the UIHandle and TrackPanelCell protocols, but...

...no actions reimplemented to them yet.

Later commits will move special cases one at a time from TrackPanel, preserving
all click and drag capabilities at each step.  With a few exceptions, but those
lost abilities are restored in yet later commits.  (Ctrl+Click on the Label
track being one.)

src/tracks/timetrack/ui/TimeTrackVRulerControls.cpp

@@ -0,0 +1,28 @@
+/**********************************************************************
+
+Audacity: A Digital Audio Editor
+
+TimeTrackVRulerControls.cpp
+
+Paul Licameli split from TrackPanel.cpp
+
+**********************************************************************/
+
+#include "../../../Audacity.h"
+#include "TimeTrackVRulerControls.h"
+#include "../../../HitTestResult.h"
+
+TimeTrackVRulerControls::TimeTrackVRulerControls()
+   : TrackVRulerControls()
+{
+}
+
+TimeTrackVRulerControls &TimeTrackVRulerControls::Instance()
+{
+   static TimeTrackVRulerControls instance;
+   return instance;
+}
+
+TimeTrackVRulerControls::~TimeTrackVRulerControls()
+{
+}