Regression range points to 28392ab1968199b7d448c1868aebabdea99318d4.

Yep, this is a corner case with the handling of weak lists during instantiation.

mtrofin@ had a GC-based solution for this before, but I will find a solution for this without an explicit GC tomorrow.

Fix available, 
https://codereview.chromium.org/2371403003/
(incl. regression test)

The following revision refers to this bug:
  https://chromium.googlesource.com/v8/v8.git/+/aff5ab11321d9a9d297260d32d0a004bd348913d

commit aff5ab11321d9a9d297260d32d0a004bd348913d
Author: mtrofin <mtrofin@chromium.org>
Date: Thu Sep 29 04:24:18 2016

[wasm] fix for GC during instantiation.

BUG= chromium:651070 

Review-Url: https://codereview.chromium.org/2371403003
Cr-Commit-Position: refs/heads/master@{#39848}

[modify] https://crrev.com/aff5ab11321d9a9d297260d32d0a004bd348913d/src/wasm/wasm-module.cc
[add] https://crrev.com/aff5ab11321d9a9d297260d32d0a004bd348913d/test/mjsunit/regress/wasm/regression-02862.js

ClusterFuzz has detected this issue as fixed in range 39837:39838.

Detailed report: https://cluster-fuzz.appspot.com/testcase?key=5090414011088896

Fuzzer: mbarbella_js_mutation
Job Type: linux_asan_d8_v8_mipsel_dbg
Platform Id: linux

Crash Type: CHECK failure
Crash Address: 
Crash State:
  next->value()->IsFixedArray() in wasm-module.cc
  
Regressed: V8: r39794:39795
Fixed: V8: r39837:39838

Minimized Testcase (2.05 Kb): https://cluster-fuzz.appspot.com/download/AMIfv94gztVoGcERY9nTmXCuihHp-28HwgbCo47KmsF74cVRK_VVDueYiihGxjnCqPZY8t8JASdTAbxe05gKK4102bBdmh09lNy40UXqkejfIZTq_BS3WA5eBV_XoQOFuVx3IOq9sx8OdOovwIhD9gLv3iZauvDrJw?testcase_id=5090414011088896

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