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Summary:
Since iOS 9.1, the keyboard is sometimes incorrectly automatically dismissed when switching between two apps that have the keyboard open, leaving one app in a confused - no-keyboard state often.

Steps to Reproduce:
1. Open Calendar.app
2. Tap on '+' to open the 'New event' screen
3. focus the 'Title' field and see the keyboard show up
4. go back to the homescreen
5. Open Contacts.app
6. Tap on '+' to open the 'New Contact' screen
7. focus the 'Name' field and see the keyboard show up
8. Double-tap the home button to go into the multitasking launcher
9. See that both apps show the keyboard in their preview
10. switch back to Calendar.app

Expected Results:
- Calendar.app would still have the keyboard visible, with the title field as first responder

Actual Results:
- Calendar.app no longer has the keyboard visible and the title field does not show a cursor

Regression:
This didn’t happen in iOS8. It also doesn’t happen when switching between one app with the keyboard open and another app with no keyboard visible and back. The keyboard stays up in the first app in that case.

Notes:
- Calling becomeFirstResponder in applicationDidBecomeActive: does not seem to help neither.