[Core] Layout Padding update issue

[myroot]

Description

The Padding of Layout does not update until re-layouting if Layout size was not changed.

Here is the code when Padding property was updated

Xamarin.Forms/Xamarin.Forms.Core/Layout.cs

Lines 103 to 106 in ded3d0f

	void IPaddingElement.OnPaddingPropertyChanged(Thickness oldValue, Thickness newValue)
	{
	InvalidateMeasureInternal(InvalidationTrigger.MeasureChanged);
	}

It only call InvalidateMeasureInternal(InvalidationTrigger.MeasureChanged); it will try to measure.
but, if size was not changed, children does not re-arranged.

Steps to Reproduce

new StackLayout
{
      HeightRequest = 200,
      Children = 
      { 
            new StackLayout
            {
                  HorizontalOptions = LayoutOptions.FillAndExpand,
                  VerticalOptions = LayoutOptions.FillAndExpand,
                  BackgroundColor = Color.Blue,
                  Children =
                  {
                        new BoxView
                        {
                              HorizontalOptions = LayoutOptions.Start,
                              Color = Color.Red,
                              HeightRequest = 100,
                              WidthRequest = 100,
                        }
                  }
            }
      }
}

Change a Padding value of Layout

Expected Behavior

inner box should be re-arranged

Actual Behavior

No change looks

Basic Information

• Version with issue: Latest
• Last known good version: before 3.1.0
• IDE:
• Platform Target Frameworks:
  • iOS:
  • Android:
  • UWP:
• Android Support Library Version:
• Nuget Packages:
• Affected Devices: All

Screenshots

Reproduction Link

https://gist.github.com/myroot/8ce0fa1bb6a017456c374e78f440625b