Could not find exact culprit CL using regression range and code search.
Adding few devs for further triaging. could someone please look into the issue.
Thank you

Using Code Search for the file, "Worklet.cpp", assigning to the concern owner.
Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/f1e393e2cab401597d52fe9b7ed90946c5d426d3

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

I can reproduce this and have a WIP fix.

A CL is under review: https://codereview.chromium.org/2697243003/

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5989961e2951701ff4a2d74bde290a0d26b45370

commit 5989961e2951701ff4a2d74bde290a0d26b45370
Author: nhiroki <nhiroki@chromium.org>
Date: Thu Feb 16 15:30:55 2017

Worklet: Avoid import() on a detached frame

Without this fix, import() on a detached frame eventually crashes because of
a null execution context.

BUG= 689265 

Review-Url: https://codereview.chromium.org/2697243003
Cr-Commit-Position: refs/heads/master@{#450972}

[add] https://crrev.com/5989961e2951701ff4a2d74bde290a0d26b45370/third_party/WebKit/LayoutTests/http/tests/worklet/chromium/README.txt
[add] https://crrev.com/5989961e2951701ff4a2d74bde290a0d26b45370/third_party/WebKit/LayoutTests/http/tests/worklet/chromium/import-on-detached-iframe.html
[add] https://crrev.com/5989961e2951701ff4a2d74bde290a0d26b45370/third_party/WebKit/LayoutTests/http/tests/worklet/chromium/resources/blank.html
[add] https://crrev.com/5989961e2951701ff4a2d74bde290a0d26b45370/third_party/WebKit/LayoutTests/http/tests/worklet/chromium/resources/empty-worklet-script.js
[modify] https://crrev.com/5989961e2951701ff4a2d74bde290a0d26b45370/third_party/WebKit/Source/core/workers/Worklet.cpp

ClusterFuzz has detected this issue as fixed in range 450943:450980.

Detailed report: https://cluster-fuzz.appspot.com/testcase?key=5168550932381696

Fuzzer: inferno_twister
Job Type: mac_asan_content_shell
Platform Id: mac

Crash Type: UNKNOWN READ
Crash Address: 0x000000000000
Crash State:
  blink::ExecutionContext::completeURL
  blink::Worklet::import
  blink::V8Worklet::importMethodCallback
  
Sanitizer: address (ASAN)

Regressed: https://cluster-fuzz.appspot.com/revisions?job=mac_asan_content_shell&range=446721:447186
Fixed: https://cluster-fuzz.appspot.com/revisions?job=mac_asan_content_shell&range=450943:450980

Reproducer Testcase: https://cluster-fuzz.appspot.com/download/AMIfv97VeNkIB4xELTH7tCV48YRC2yJWVVyFL9uxrn2t6bmLMKzAe1_3bT6tyP12Zq-L5XaynGa6IxWY3kYVf2TIwFMQKSfFfwfPXbr734H-KOXfBPHVSbZBUlxsoHoug0ILeYDCkSBB_8GDQgc_Y_bTqqly_o9gM6YOG9kd1gAy0OWHPg6c5yQ2GXgpvq9Rb1G_e0Lkw3j-1C_iYMniXhjbSfZ3tGS82QIJBQeC9w39xP55_qd2WajsDjMW_JuV_bb06vYtc--hd-hQDp7NFqosBmG1k6E9BrKO6PMRqMQIG-oRCD1tkTPW78CereIIISCfhPGPz3q259i2OsE4ZeCrcveFtMvb1hOWrIG41Ie6uMufwMOfYGw?testcase_id=5168550932381696


See https://dev.chromium.org/Home/chromium-security/bugs/reproducing-clusterfuzz-bugs for more information.

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

It looks like my patch is working well. I'll close this.