Centered flood fill style ink drop ripples on mouse/touch points.

ui/events/event.h

Index: ui/events/event.h
diff --git a/ui/events/event.h b/ui/events/event.h
index b01c12d3e303aacd6bec1c75a5b9e911a0c8a028..e0961d1365f828d7d191c80ce6f89469f6645d0f 100644
--- a/ui/events/event.h
+++ b/ui/events/event.h
@@ -318,6 +318,13 @@ class EVENTS_EXPORT CancelModeEvent : public Event {
 
 class EVENTS_EXPORT LocatedEvent : public Event {
  public:
+  // Convenience function that casts |event| to a LocatedEvent if it is one,
+  // otherwise returns null.
+  static const ui::LocatedEvent* AsLocatedEventIfLocatedEvent(
+      const ui::Event* event) {
+    return event && event->IsLocatedEvent() ? event->AsLocatedEvent() : nullptr;
+  }
+
   ~LocatedEvent() override;
 
   float x() const { return location_.x(); }