ToggleMenuFlyoutItem and RadioMenuFlyoutItem do not show assigned icon in winui 2.6 prerelease

[lhak]

Describe the bug

When using the new styles for both controls, the assigned icon is ignored.

Steps to reproduce the bug

Steps to reproduce the behavior:

1. Create a new winui 2.6 app and change the styles version to "latest"
2. Add a ToggleMenuFlyoutItem or RadioMenuFlyoutItem
3. Assign an icon to the item
4. Observe that the icon is not shown

Expected behavior

Icon should be shown

Screenshots

Version Info

NuGet package version:

[Microsoft.UI.Xaml.2.6.0-prerelease.210227001]

Windows app type:

UWP	Win32
Yes

Windows 10 version	Saw the problem?
Insider Build (xxxxx)
October 2020 Update (19042)	Yes
May 2020 Update (19041)
November 2019 Update (18363)
May 2019 Update (18362)
October 2018 Update (17763)
April 2018 Update (17134)
Fall Creators Update (16299)
Creators Update (15063)

Device form factor	Saw the problem?
Desktop	Yes
Xbox
Surface Hub
IoT

Additional context

[ranjeshj]

@lhak can you paste a screenshot / markup ?

[StephenLPeters]

@tashatitova and @ranjeshj it looks like we removed the ViewBox which was containing the icons on accident. Here is the line from the PR that removed it #3958 (comment)

[tashatitova]

@StephenLPeters @ranjeshj yes, accidental removal while cleaning up Reveal. Wasn't caught in testing. Need to add highlighted lines back.

[marcelwgn]

Taking a look at this.