Merge the android-9.0.0_r55 release tag
Android 9.0.0 Release 55 (6197209)

* tag 'android-9.0.0_r55':
  AOSP/UnifiedEmail - bug fix: do not allow composing message with hidden private data attachments - Switch intent filtering to be blacklist based rather than whitelist based.
  AOSP/UnifiedEmail - Secure UPDATE_WIDGET receiver with a new permission

Change-Id: I9ce5cafa808daba53daaa3392228051094e596d8