Add 'android/playground/' from commit 'bc0f66d940262dbb23f7d110722bc0524ed44647'

git-subtree-dir: android/playground
git-subtree-mainline: d1937cbcfb25c713a7c39feeed41aa86724273d8
git-subtree-split: bc0f66d940262dbb23f7d110722bc0524ed44647
tree: 89206c04793d05afe760c91ea6bb14bdd11b76ac
  1. android/
  2. README.md
README.md