Fix isStandalone when PWA entering fullscreen (#156424)
Fix isStandalone when PWA entering fullscreen (#156424)

Fixes https://github.com/microsoft/vscode/issues/156347
microsoft/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode