Import downloader code to AOSP. am: c0449c8753 am: 3ebc998629

Original change: https://android-review.googlesource.com/c/platform/external/downloader/+/1591311

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Id6fceb6c08bcd09d75d550f8e8754b2f8375bc7f
tree: 5895b1324176d6021865c54215b35fc311ae4544
  1. src/
  2. LICENSE
  3. METADATA
  4. MODULE_LICENSE_APACHE2
  5. OWNERS