Port active map / cyclic refresh fixes to VP10.

Bring commits 575e81f and 3d6b8a6 to VP10. These changes predate
the creation of the active map cyclic refresh test.

BUG=https://bugs.chromium.org/p/webm/issues/detail?id=1224

Change-Id: I3559b6933ffa5649926a4b214e45ed0fae523a25
2 files changed