MacViews: Reveal scrollbars when resting on the trackpad.

ui/events/test/event_generator.h

Index: ui/events/test/event_generator.h
diff --git a/ui/events/test/event_generator.h b/ui/events/test/event_generator.h
index 039acbb8ec5fb95cced1324fbd97bd0cb782487d..f91143662e94f5e7867bc2a9c90438c4087e187c 100644
--- a/ui/events/test/event_generator.h
+++ b/ui/events/test/event_generator.h
@@ -350,6 +350,15 @@ class EventGenerator {
                       const std::vector<gfx::PointF>& offsets,
                       int num_fingers);
 
+  // Generate a TrackPad "rest" event. That is, a user resting fingers on the
+  // trackpad without moving. This may then be followed by a ScrollSequence(),
+  // or a CancelTrackpadRest().
+  void GenerateTrackpadRest();
+
+  // Cancels a previous GenerateTrackpadRest(). That is, a user lifting fingers
+  // from the trackpad without having moved them in any direction.
+  void CancelTrackpadRest();
+
   // Generates a key press event. On platforms except Windows and X11, a key
   // event without native_event() is generated. Note that ui::EF_ flags should
   // be passed as |flags|, not the native ones like 'ShiftMask' in <X11/X.h>.