ChipsControl.cs

 public static readonly BindableProperty ChipTextProperty = BindableProperty.Create("ChipText", typeof(string), typeof(ChipsControl), default(string),defaultBindingMode:BindingMode.TwoWay,propertyChanged:ChipTextPropertyChanged);

        private static void ChipTextPropertyChanged(BindableObject bindable, object oldValue, object newValue)
        {
            var control = (ChipsControl)bindable;
            control.ChipText = newValue.ToString();
        }

        public string ChipText
        {
            get { return (string)GetValue(ChipTextProperty); }
            set { SetValue(ChipTextProperty, value); }
        }