Remove ObserveWheelEventAndResult callbacks since they are now gesture based.

ui/events/blink/input_scroll_elasticity_controller.h

Index: ui/events/blink/input_scroll_elasticity_controller.h
diff --git a/ui/events/blink/input_scroll_elasticity_controller.h b/ui/events/blink/input_scroll_elasticity_controller.h
index 915b2e88af12cd7ee2e5a492e3a7f000f3f0c539..bbbc445a6d87ecaa11ca4b6cf32e6725d399b698 100644
--- a/ui/events/blink/input_scroll_elasticity_controller.h
+++ b/ui/events/blink/input_scroll_elasticity_controller.h
@@ -50,14 +50,6 @@ class InputScrollElasticityController {
 
   base::WeakPtr<InputScrollElasticityController> GetWeakPtr();
 
-  // Update the overscroll state based a wheel event that has been processed.
-  // Note that this assumes that all events are coming from a single input
-  // device. If the user simultaneously uses multiple input devices, Cocoa may
-  // not correctly pass all the gesture begin and end events. In this case,
-  // this class may disregard some scrolls that come in at unexpected times.
-  void ObserveWheelEventAndResult(
-      const blink::WebMouseWheelEvent& wheel_event,
-      const cc::InputHandlerScrollResult& scroll_result);
   // Update the overscroll state based a gesture event that has been processed.
   // Note that this assumes that all events are coming from a single input
   // device. If the user simultaneously uses multiple input devices, Cocoa may