Creating a window shows it before calling .Show() and .Hide() does not work

[Jacalz]

Describe the bug:

Creating a second window and building using the mobile driver shows the second window without every calling .Show() on the second window. The only way to avoid showing the window is to explicitly close it. Calling .Hide() leaves the first window not rendering at all.

To Reproduce:

Steps to reproduce the behaviour:

1. Run the example code using go run -tags mobile main.go
2. Close the second window by adding w2.Close()
3. Run the modified example code using go run -tags mobile main.go
4. Change the w2.Close() call to w2.Hide()
5. Run the modified example code using go run -tags mobile main.go

Screenshots:

Example code:

package main

import (
	"fyne.io/fyne/v2/app"
	"fyne.io/fyne/v2/container"
	"fyne.io/fyne/v2/widget"
)

func main() {
	a := app.New()
	w := a.NewWindow("Hello")

	w2 := a.NewWindow("Second")
	w2.SetContent(widget.NewLabel("Second window"))

	hello := widget.NewLabel("Hello Fyne!")
	w.SetContent(container.NewVBox(
		hello,
		widget.NewButton("Hi!", func() {
			hello.SetText("Welcome :)")
		}),
	))

	w.ShowAndRun()
}

Device (please complete the following information):

• OS: Linux (-tags mobile) and Android have been tested
• Version: 5.10.6
• Go version: 1.15.6 and 1.13.8
• Fyne version: 2.0.0-rc5

[andydotxyz]

On develop and will be in 2.0.1 release