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

Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/5db093f59a68e29ed89a115da7e0c86b897a67b1

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

@junov is the right one. :)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/36c0abdab86cc8d2717b75c46587f1c23c9ad032

commit 36c0abdab86cc8d2717b75c46587f1c23c9ad032
Author: Justin Novosad <junov@chromium.org>
Date: Wed Aug 09 14:39:06 2017

Add null pointer check in OffscreenCanvas::GetOrCreateImageBuffer

BUG= 752770 

Change-Id: Id046e6a772bd456652862ca6c14b74469d613ed9
Reviewed-on: https://chromium-review.googlesource.com/607039
Commit-Queue: Fernando Serboncini <fserb@chromium.org>
Reviewed-by: Fernando Serboncini <fserb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#492970}
[modify] https://crrev.com/36c0abdab86cc8d2717b75c46587f1c23c9ad032/third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.cpp

ClusterFuzz has detected this issue as fixed in range 492866:493084.

Detailed report: https://clusterfuzz.com/testcase?key=5204731390853120

Fuzzer: inferno_twister
Job Type: linux_asan_content_shell_drt
Platform Id: linux

Crash Type: Null-dereference READ
Crash Address: 0x000000000020
Crash State:
  blink::OffscreenCanvas::GetOrCreateImageBuffer
  blink::OffscreenCanvasRenderingContext2D::commit
  blink::V8OffscreenCanvasRenderingContext2D::commitMethodCallback
  
Sanitizer: address (ASAN)

Regressed: https://clusterfuzz.com/revisions?job=linux_asan_content_shell_drt&range=473072:473106
Fixed: https://clusterfuzz.com/revisions?job=linux_asan_content_shell_drt&range=492866:493084

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5204731390853120

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.

ClusterFuzz testcase 5204731390853120 is verified as fixed, so closing issue as verified.

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