Deprecation: #78279 - Deprecate top.TYPO3.Backend.ContentContainer.iframe 

See forge#78279

Description 

The property top.TYPO3.Backend.ContentContainer.iframe has been marked as deprecated.

Impact 

Using this property will stop working in TYPO3 v9.

Affected Installations 

All installations using top.TYPO3.Backend.ContentContainer.iframe.

Migration 

Use accessor method top.TYPO3.Backend.ContentContainer.get() instead.