Fix freeze rate calculations am: 2a3af65a am: 10d0ec43

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/av/+/23352136



Change-Id: I0c791f7d7175f804b16044438f9d20669a3d487f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>