Overhaul Mandoline event transport code

ui/mojo/events/input_event_constants.mojom

Index: ui/mojo/events/input_event_constants.mojom
diff --git a/ui/mojo/events/input_event_constants.mojom b/ui/mojo/events/input_event_constants.mojom
index b3e0ea1f663ef3f2009d200bf22859aa8ada5688..ed69f92c31c83d08e6c11615fcf5a63d35b2c91b 100644
--- a/ui/mojo/events/input_event_constants.mojom
+++ b/ui/mojo/events/input_event_constants.mojom
@@ -41,6 +41,16 @@ enum MouseEventFlags {
 };
 
 enum PointerKind {
-  TOUCH,
+  UNKNOWN,
   MOUSE,
+  PEN,
+  TOUCH,
+  WHEEL,

[sadrul, 2015/09/09 04:19:04]

Do we need 'wheel' as a separate kind? e.g. both mouse and pen can send wheel
events I think?

[rjkroege, 2015/09/09 19:45:38]

Based on http://www.w3.org/TR/pointerevents/#pointerevent-interface and the DOM
level 3 spec, I think that it's reasonable to make them separate. But I may have
(mis)read the wrong specs.

[sadrul, 2015/09/10 17:39:15]

I am not sure. I feel like the event-type should be sufficient here, and the
PointerKind would be more useful as an indication of what kind of device it
originated from (so it could be used to treat events coming from a normal mouse
differently than events coming from a touchpad). If we use WHEEL for both of
these kinds of events, we would lose that information.

[rjkroege, 2015/09/12 01:29:02]

I agree. In Web spec land, Pointer encompasses touch, pen, mouse. while Wheel is
completely separate.

I made wheel a new kind of top-level event distinct from Pointer. 

+};
+
+enum WheelMode {
+  PIXEL,
+  LINE,
+  PAGE,
+  SCALING,
 };