The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/49cab7bcd1dd263fd9303a831b9465312567c50a

commit 49cab7bcd1dd263fd9303a831b9465312567c50a
Author: valih <valih@google.com>
Date: Tue Nov 08 02:55:43 2016

DevTools: fix a crash in stopRuleUsageTracking

stopRuleUsageTracking used to crash on the NTP.

BUG= 663034 

Review-Url: https://codereview.chromium.org/2484903002
Cr-Commit-Position: refs/heads/master@{#430491}

[add] https://crrev.com/49cab7bcd1dd263fd9303a831b9465312567c50a/third_party/WebKit/LayoutTests/inspector-protocol/css/cssom-modify-rule-and-get-rule-list-expected.txt
[add] https://crrev.com/49cab7bcd1dd263fd9303a831b9465312567c50a/third_party/WebKit/LayoutTests/inspector-protocol/css/cssom-modify-rule-and-get-rule-list.html
[modify] https://crrev.com/49cab7bcd1dd263fd9303a831b9465312567c50a/third_party/WebKit/Source/core/inspector/InspectorCSSAgent.cpp
[modify] https://crrev.com/49cab7bcd1dd263fd9303a831b9465312567c50a/third_party/WebKit/Source/core/inspector/InspectorStyleSheet.cpp

valih@, could you please mark it as 'Fixed' in case if there is no pending work to be done?

Thank you!

Assigning owner since @caseq works closest with valih.

@valih: for reference, could you add reproduction steps for the bug here?

This should be fixed by the commit referenced above.