Roll third_party/wuffs to version 0.3.0-alpha.15

Change-Id: If313aa305b82d85d2260538a896d306a4bb89c3b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2426143Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Nigel Tao <nigeltao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809972}

DEPS

@@ -334,7 +334,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling wuffs
   # and whatever else without interference from each other.
-  'wuffs_revision': '3e8cb4ebf8a0b024549e1086c7ed65d5df0fe8fa',
+  'wuffs_revision': 'aa46859ea40c72516deffa1b146121952d6dfd3b',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling libgifcodec
   # and whatever else without interference from each other.

third_party/wuffs/README.chromium

 Name: Wuffs (Wrangling Untrusted File Formats Safely)
 Short name: Wuffs
 URL: https://github.com/google/wuffs
-Version: 0.3.0-alpha.14
-Revision: 3e8cb4ebf8a0b024549e1086c7ed65d5df0fe8fa
+Version: 0.3.0-alpha.15
+Revision: aa46859ea40c72516deffa1b146121952d6dfd3b
 Security critical: yes
 License: Apache 2.0