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..326d7a595161dc1b3c3226b5544eb845fc568326 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 TrackpadRest();

[sky, 2016/11/15 14:19:51]

optional: for clarity name this GenerateTrackpadReset.

[tapted, 2016/11/16 02:54:45]

Done.

+
+  // Cancels a previous TrackpadRest(). 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>.