Merge "Upgrade libwebm to 485fb67b324aec5298765e899dc054459d3946e5" am: 0428151ec8

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

Change-Id: I9dc4946c9db10c5b5e7ea68df77259d60a443607