WebContentsAdapter::initialize might hold a ref on the wrong BrowserContextAdapter after a newWindowRequest

To reproduce the crash:

• Open quicktestbrowser and find a link that opens a new tab automatically (like the Digia link at the bottom of qt.io)
• Open that link to open in a new BrowserWindow (which creates a new WebEngineProfile)
• Do it again to open 4-5 windows
• Close the first window (containing all refs to the BrowserContext that was set behind the scene on the adopted content::WebContents)
• Wait a bit, close all other windows

Stack trace attached

Discussed solution was to ignore with a warning when setting a different WebEngineProfile on an adopted WebEngineView.