Merge "libbinder: finish{F,Unf}lattenBinder symmetry" am: 8662ab7f4b am: d0a4e0e9dc am: b6f012081c

Original change: https://android-review.googlesource.com/c/platform/frameworks/native/+/1514934

Change-Id: I57c1f203f2ce4e85e61feffac8bf62e2854a1d47