Roll src/third_party/libavif/src/ 3fd2db22e..94ac5b4c7 (3 commits)

https://chromium.googlesource.com/external/github.com/AOMediaCodec/libavif.git/+log/3fd2db22eef9..94ac5b4c7215

$ git log 3fd2db22e..94ac5b4c7 --date=short --no-merges --format='%ad %ae %s'
2020-08-19 wtc Update another matrix coeffs default to BT.601
2020-08-19 jdrago Update the default matrixCoefficients for avifenc to match ISO/IEC 23000-22:2019 Amendment 2
2020-08-19 jdrago Adjust fallback YUV coefficients based on upcoming MIAF Amendment 2, fix typo in coeffs table

Created with:
  roll-dep src/third_party/libavif/src
R=dalecurtis@chromium.org

Bug: 1119465
Change-Id: I2ef7ceed322ebb9cebf605afdab82ebfe7c25b64
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2365366
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#800001}

DEPS

@@ -342,7 +342,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling libavif
   # and whatever else without interference from each other.
-  'libavif_revision': '3fd2db22eef9fbd20bc5f768b50f13102ec77f7c',
+  'libavif_revision': '94ac5b4c721597f739ee4b6fadee5c56bf952c73',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling nearby
   # and whatever else without interference from each other.