Merge "Upgrade libwebm to 485fb67b324aec5298765e899dc054459d3946e5" am: 0428151ec8 am: 1a5a14f484 am: c52e98a9c1

Original change: https://android-review.googlesource.com/c/platform/external/libwebm/+/1510523

Change-Id: I3b514d920f315234a6ca0b8f4b3a5009dd0b9b51