Roll src/third_party/libavif/src/ 4cfee6282..fdc636b4c (12 commits)

https://chromium.googlesource.com/external/github.com/AOMediaCodec/libavif.git/+log/4cfee6282b97..fdc636b4ce09

$ git log 4cfee6282..fdc636b4c --date=short --no-merges --format='%ad %ae %s'
2020-08-12 wtc Use fullSize for alpha in avifImageAllocatePlanes
2020-08-12 wtc Check for grid images consistently
2020-08-12 wtc Clean up avifDecoderReset()
2020-08-12 wtc Fix avifDecoderDataFillImageGrid for alpha images
2020-08-12 wtc Change conditional expressions to prevalent style (#273)
2020-08-12 wtc Validate grid image size and tile size (#272)
2020-08-12 wtc Ignore clang -Wc11-extensions warnings on dav1d.h (#271)
2020-08-12 52529860+novomesk Disable Clang warning (drop const qualifier) (#270)
2020-08-12 wtc avifParseImageGridBox should consume all item data (#269)
2020-08-12 wtc Declare local variable 'alphaTile' in if statement (#268)
2020-08-11 wtc Use local var 'data' throughout avifDecoderReset (#266)
2020-08-11 wtc Disallow zero grid output_width or output_height (#265)

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

Change-Id: I78507ef6bc038cdb7a96dad09cd5ae65e3a89c8e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2354613Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Wan-Teh Chang <wtc@google.com>
Cr-Commit-Position: refs/heads/master@{#797790}

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': '4cfee6282b97533e6c99183ddf7a897173755c69',
+  'libavif_revision': 'fdc636b4ce090f235e84404b6161fa140eb86d38',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling nearby
   # and whatever else without interference from each other.