DO NOT MERGE libvpx: Cherry-pick 8b4c315 from upstream am: 5225d939bb am: 1447f3c123  -s ours am: 47c6ca5084  -s ours am: 6ef2aa9bda  -s ours am: 8961d3eb51 am: 9b65b54f89 am: 1361c7742f  -s ours am: 1f53523f7e am: fa9ba7dd89 am: c8795980b1
am: 7f3769b1d9  -s ours

Change-Id: I1cbe2be2653bead4f29e03a6fb618b5e802b0df7