Chris: this error is in a test you added in commit cb8aa76 at "2016-08-24 11:51:34".  Can you please investigate?  If you can't find the error in the next 30 minutes please disable test or revert CL.  Thanks.

Commit:
https://chromium.googlesource.com/chromium/src/+/cb8aa763196dbb73c7aa724bd3bc7374a2a540a7

Error:
AssertionError: expected true to be false
    at Function.assert.isFalse (chai.js:2459:31)
    at assertFalse (test_api.js:860:17)
    at history_list_test.js:308:11

Test line:
https://cs.chromium.org/chromium/src/chrome/test/data/webui/md_history/history_list_test.js?rcl=0&l=308

in test 'scrolling history list causes toolbar shadow to appear'.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/62514ae903a294ca3f3075b0f8c452d53d02da0a

commit 62514ae903a294ca3f3075b0f8c452d53d02da0a
Author: calamity <calamity@chromium.org>
Date: Fri Aug 26 08:46:56 2016

[MD History] Disable toolbar shadow test.

This CL disables the toolbar shadow test because it's flaky. This will be
reenabled after investigation.

BUG= 640862 

Review-Url: https://codereview.chromium.org/2271583009
Cr-Commit-Position: refs/heads/master@{#414673}

[modify] https://crrev.com/62514ae903a294ca3f3075b0f8c452d53d02da0a/chrome/test/data/webui/md_history/history_list_test.js

Detected 3 new flakes for test/step "MaterialHistoryBrowserTest.HistoryListTest". To see the actual flakes, please visit https://chromium-try-flakes.appspot.com/all_flake_occurrences?key=ahVzfmNocm9taXVtLXRyeS1mbGFrZXNyNQsSBUZsYWtlIipNYXRlcmlhbEhpc3RvcnlCcm93c2VyVGVzdC5IaXN0b3J5TGlzdFRlc3QM. This message was posted automatically by the chromium-try-flakes app. Since flakiness is ongoing, the issue was moved back into Sheriff Bug Queue (unless already there).

Detected 3 new flakes for test/step "MaterialHistoryBrowserTest.HistoryListTest". To see the actual flakes, please visit https://chromium-try-flakes.appspot.com/all_flake_occurrences?key=ahVzfmNocm9taXVtLXRyeS1mbGFrZXNyNQsSBUZsYWtlIipNYXRlcmlhbEhpc3RvcnlCcm93c2VyVGVzdC5IaXN0b3J5TGlzdFRlc3QM. This message was posted automatically by the chromium-try-flakes app.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f967bf2701c41f0f074e3ea2b664d73a0085125b

commit f967bf2701c41f0f074e3ea2b664d73a0085125b
Author: xidachen <xidachen@chromium.org>
Date: Mon Oct 31 13:42:03 2016

Disable MaterialHistoryBrowserTest.HistoryListTest since

New flakes detected on chromeos

BUG= 640862 
TBR=calamity@chromium.org
NOTRY=true

Review-Url: https://codereview.chromium.org/2459263003
Cr-Commit-Position: refs/heads/master@{#428698}

[modify] https://crrev.com/f967bf2701c41f0f074e3ea2b664d73a0085125b/chrome/test/data/webui/md_history/md_history_browsertest.js

Hi Sheriff here,

The MaterialHistoryBrowserTest.SyncedTabsTest fails on Mac, will disable it, please investigate and re-enable.

Link to mac failure:
https://build.chromium.org/p/chromium.mac/builders/Mac10.11%20Tests/builds/3059

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/53f02e124e3a0369a7fb3724fda80f614887e373

commit 53f02e124e3a0369a7fb3724fda80f614887e373
Author: xidachen <xidachen@chromium.org>
Date: Mon Oct 31 14:08:32 2016

Disable MaterialHistoryBrowserTest.SyncedTabsTest

It fails on Mac

BUG= 640862 
TBR=calamity@chromium.org
NOTRY=true

Review-Url: https://codereview.chromium.org/2459383002
Cr-Commit-Position: refs/heads/master@{#428701}

[modify] https://crrev.com/53f02e124e3a0369a7fb3724fda80f614887e373/chrome/test/data/webui/md_history/md_history_browsertest.js

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e31e1d7de8773afa0f5b5a2fa7b43e05ab9c3eb6

commit e31e1d7de8773afa0f5b5a2fa7b43e05ab9c3eb6
Author: calamity <calamity@chromium.org>
Date: Wed Nov 02 02:52:48 2016

Revert of Disable MaterialHistoryBrowserTest.HistoryListTest since (patchset #1 id:1 of https://codereview.chromium.org/2459263003/ )

Reason for revert:
Looks like this was a skia misconfig that was causing too much output.

Original issue's description:
> Disable MaterialHistoryBrowserTest.HistoryListTest since
>
> New flakes detected on chromeos
>
> BUG= 640862 
> TBR=calamity@chromium.org
> NOTRY=true
>
> Committed: https://crrev.com/f967bf2701c41f0f074e3ea2b664d73a0085125b
> Cr-Commit-Position: refs/heads/master@{#428698}

TBR=xidachen@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG= 640862 

Review-Url: https://codereview.chromium.org/2466263005
Cr-Commit-Position: refs/heads/master@{#429192}

[modify] https://crrev.com/e31e1d7de8773afa0f5b5a2fa7b43e05ab9c3eb6/chrome/test/data/webui/md_history/md_history_browsertest.js

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/dd157d9a5f102bb94928e7a2be61250e2ff43826

commit dd157d9a5f102bb94928e7a2be61250e2ff43826
Author: calamity <calamity@chromium.org>
Date: Fri Dec 16 07:05:32 2016

[MD History] Reenable SyncedTabsTest.

This CL skips the focus test that is likely the cause of failures and
reenables the test on all platforms.

BUG= 640862 

Review-Url: https://codereview.chromium.org/2582543005
Cr-Commit-Position: refs/heads/master@{#439056}

[modify] https://crrev.com/dd157d9a5f102bb94928e7a2be61250e2ff43826/chrome/test/data/webui/md_history/history_synced_tabs_test.js
[modify] https://crrev.com/dd157d9a5f102bb94928e7a2be61250e2ff43826/chrome/test/data/webui/md_history/md_history_browsertest.js

Flakes seem gone. Reopen if this is still an issue.