Don't fade in overlay scrollbar when user interacting the content under scrollbar.

ui/events/blink/input_handler_proxy.cc

Index: ui/events/blink/input_handler_proxy.cc
diff --git a/ui/events/blink/input_handler_proxy.cc b/ui/events/blink/input_handler_proxy.cc
index 6ff1983d7139c16be4b7604726a8c80db40dea7f..0eca95e9f38ab3a68feb66f23ddf51c092f8e30a 100644
--- a/ui/events/blink/input_handler_proxy.cc
+++ b/ui/events/blink/input_handler_proxy.cc
@@ -519,8 +519,11 @@ InputHandlerProxy::EventDisposition InputHandlerProxy::HandleInputEvent(
       // TODO(davemoore): This should never happen, but bug #326635 showed some
       // surprising crashes.
       CHECK(input_handler_);
+      bool is_mouse_down =
+          mouse_event.button == blink::WebMouseEvent::Button::kLeft;
       input_handler_->MouseMoveAt(gfx::Point(mouse_event.PositionInWidget().x,
-                                             mouse_event.PositionInWidget().y));
+                                             mouse_event.PositionInWidget().y),
+                                  is_mouse_down);
       return DID_NOT_HANDLE;
     }
     case WebInputEvent::kMouseLeave: {