Ignore cancel errors on import file and change import folder code to act similarly
Moved the chooser logic out of the import folder action and into the common importFolder method (so that the backdrop operates properly again).  Action just handles import job
Review fixes
reverse expression logic; fix npe; refresh folders after import
Merge pull request #3074 from dart-lang/umop-fix-import_errors

Fix import dialog errors (on cancel) and fix import folder dialog backdrop