Roll external/skia 556d5c7d4..0c9402ed8 (1 commits)

https://skia.googlesource.com/skia.git/+log/556d5c7d4..0c9402ed8

2017-06-12 msarett@google.com Encode F16 with correct color space tag

Test: Presubmit checks will test this change.

Test: CTS and Skia unit tests.
Bug: 62538716
Change-Id: I17f14ae75d4091fe589fdba6de8af0edaf6e9328