Import downloader code to AOSP. am: c0449c8753

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

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Icb13aa05f2bb079a553f39684d7ba3abebb858d7
tree: 5895b1324176d6021865c54215b35fc311ae4544
  1. src/
  2. LICENSE
  3. METADATA
  4. MODULE_LICENSE_APACHE2
  5. OWNERS