Predator and CL could not provide any possible suspects.
Using Code Search for the file, "SubresourceIntegrityHelper.cpp" assigning to the concern owner using GIT Blame.

Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/d001e0d5d89d2ecdee30c3fe951f5088fc4f3262

@hiroshige -- Could you please look into the issue, kindly re-assign if this is not related to your changes.
Thank You.

Reproduced locally on Linux.
The execution context is null.

Draft CL: https://chromium-review.googlesource.com/c/chromium/src/+/655807

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/13e0a33c0de604128233dd9e293e946070aa2f22

commit 13e0a33c0de604128233dd9e293e946070aa2f22
Author: Hiroshige Hayashizaki <hiroshige@chromium.org>
Date: Tue Sep 12 03:17:18 2017

Cancel SRIVerifier when the corresponding context is destroyed

Otherwise, DidGetReadable() is called with null ExecutionContext.

Bug:  758883 
Change-Id: I904d0c946a1be928c1fe2bebb37efec384a7bd59
Reviewed-on: https://chromium-review.googlesource.com/655807
Commit-Queue: Hiroshige Hayashizaki <hiroshige@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501166}
[modify] https://crrev.com/13e0a33c0de604128233dd9e293e946070aa2f22/third_party/WebKit/Source/modules/fetch/FetchManager.cpp

ClusterFuzz has detected this issue as fixed in range 501164:501180.

Detailed report: https://clusterfuzz.com/testcase?key=6087073131134976

Fuzzer: inferno_twister
Job Type: mac_asan_content_shell
Platform Id: mac

Crash Type: Null-dereference READ
Crash Address: 0x000000000000
Crash State:
  blink::SubresourceIntegrityHelper::DoReport
  blink::FetchManager::Loader::SRIVerifier::DidGetReadable
  content::SharedMemoryDataConsumerHandle::Context::NotifyInternal
  
Sanitizer: address (ASAN)

Fixed: https://clusterfuzz.com/revisions?job=mac_asan_content_shell&range=501164:501180

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=6087073131134976

Additional requirements: Requires HTTP

See https://github.com/google/clusterfuzz-tools for more information.

If you suspect that the result above is incorrect, try re-doing that job on the test case report page.

Fixed.

Do we need to merge to M-62?
DoReport is introduced recently, but the root cause has existed since before.

ClusterFuzz testcase 6087073131134976 is verified as fixed, so closing issue as verified.

If this is incorrect, please add ClusterFuzz-Wrong label and re-open the issue.