Add TapPacketReader#startAsyncForTest, poll am: 046d253d63 am: 97825354b8 am: 82094abeb0 am: b09abf4d91

Original change: https://android-review.googlesource.com/c/platform/frameworks/libs/net/+/1435132

Change-Id: I50f05ac06d70d3e29cf1586d25a42f93f387c879
tree: 225cba0c582e4edeac687c2cfe3bc8d9d44bdda4
  1. staticlibs/