Mac: Share kScrollbarPixelsPerCocoaTick between ui:: and blink:: events

ui/events/cocoa/cocoa_event_utils.h

Index: ui/events/cocoa/cocoa_event_utils.h
diff --git a/ui/events/cocoa/cocoa_event_utils.h b/ui/events/cocoa/cocoa_event_utils.h
index a5984357537b46e66eadcaeecb56136b30471cd8..71ddab95e788483290d3b7128bacad60d190cf2a 100644
--- a/ui/events/cocoa/cocoa_event_utils.h
+++ b/ui/events/cocoa/cocoa_event_utils.h
@@ -11,6 +11,9 @@
 
 namespace ui {
 
+// Conversion between wheel delta amounts and number of pixels to scroll.
+constexpr double kScrollbarPixelsPerCocoaTick = 40.0;

[Avi (use Gerrit), 2016/08/10 15:17:29]

Is that the new preferred style? I thought enum or exported constant was the
style.

[tapted, 2016/08/11 01:24:08]

http://go/cppguide#Use_of_constexpr is pretty much "constexpr whenever you can"
(also, e.g, http://go/cppguide#Static_and_Global_Variables ). E.g. it prevents
the compiler slipping in a static initializer you don't want. Exporting is
somewhat orthogonal -- it's still required if something takes the address --
constexpr doesn't prevent that but `enum` would. However, I avoided enum since I
would have to change it to an integral constant (which I guess it could be...
but wasn't before).

+
 // Converts the Cocoa |modifiers| bitsum into a ui::EventFlags bitsum.
 EVENTS_EXPORT int EventFlagsFromModifiers(NSUInteger modifiers);