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