I haven't done a bisect, but I suspect this CL, which introduces an early return in the _update()
https://chromium.googlesource.com/chromium/src/+/3bd2528a0f1030c043fa73b78cc2287b217a2df4

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/eda21d3879cf6451ab838530a2ca25167fa3b7c5

commit eda21d3879cf6451ab838530a2ca25167fa3b7c5
Author: Erik Luo <luoe@chromium.org>
Date: Tue Oct 17 21:59:17 2017

DevTools: error warning counter icons should not be visible by default

Error and warning counters show up by default, even when console has
no messages of those types. The counter logic already calls _update()
initially, but it results in a no-op when error/warningCount are
up-to-date by default.

This CL initializes error/warningCount differently to ensure the first
_update() will not be a no-op.

Bug:  775239 
Change-Id: I98f3c1aa0838baf70c3372c4a07781011878f8f0
Reviewed-on: https://chromium-review.googlesource.com/722077
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Erik Luo <luoe@chromium.org>
Cr-Commit-Position: refs/heads/master@{#509560}
[modify] https://crrev.com/eda21d3879cf6451ab838530a2ca25167fa3b7c5/third_party/WebKit/Source/devtools/front_end/console_counters/WarningErrorCounter.js

Your change meets the bar and is auto-approved for M63. Please go ahead and merge the CL to branch 3239 manually. Please contact milestone owner if you have questions.
Owners: cmasso@(Android), cmasso@(iOS), gkihumba@(ChromeOS), govind@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Please merge your change to M63 branch 3239 by 4:00 PM PT today, Thursday so we can take it in for next M63 dev release. Thank you.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3314bcd420784abd035ab3ffbbe28df20cc65d01

commit 3314bcd420784abd035ab3ffbbe28df20cc65d01
Author: Erik Luo <luoe@chromium.org>
Date: Thu Oct 19 17:35:37 2017

DevTools: error warning counter icons should not be visible by default

Error and warning counters show up by default, even when console has
no messages of those types. The counter logic already calls _update()
initially, but it results in a no-op when error/warningCount are
up-to-date by default.

This CL initializes error/warningCount differently to ensure the first
_update() will not be a no-op.

Bug:  775239 
Change-Id: I98f3c1aa0838baf70c3372c4a07781011878f8f0
Reviewed-on: https://chromium-review.googlesource.com/722077
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Erik Luo <luoe@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#509560}(cherry picked from commit eda21d3879cf6451ab838530a2ca25167fa3b7c5)
Reviewed-on: https://chromium-review.googlesource.com/728401
Reviewed-by: Erik Luo <luoe@chromium.org>
Cr-Commit-Position: refs/branch-heads/3239@{#70}
Cr-Branched-From: adb61db19020ed8ecee5e91b1a0ea4c924ae2988-refs/heads/master@{#508578}
[modify] https://crrev.com/3314bcd420784abd035ab3ffbbe28df20cc65d01/third_party/WebKit/Source/devtools/front_end/console_counters/WarningErrorCounter.js

Thanks for the headsup, should be merged now.

 Issue 775452  has been merged into this issue.

Tested the issue on Win-10, mac 10.12.6 and Ubuntu 14.04 using chrome version #63.0.3239.15 as per the merged issue:  775452 .
Note: Couldn't verify the issue using chrome version #63.0.3239.16 due to the blocking issue:  777720 .

Observed that error/warning icons are still visible on dev tools.
Attached a screenshot for reference

luoe@ - Could you please check the screenshot and please confirm the expected behavior and the fix.

Thanks...!!

Deleted: 775239.png 648 KB

	775239.png 648 KB View Download

Correction: The above behaviour at comment #9 is for only OS-Win and OS-Mac.

In OS-Linux, the error/warning icons were not visible as per the attached screen shot(775239.png).

Thanks...!!

Deleted: 775239.png 227 KB

	775239.png 227 KB View Download

The screenshot in comment #9 behavior looks fine to me since it's on the newtab page.  More specifically, the bug occurs only when visiting a page that has 0 errors/warnings, so using a page like `about:blank` would be a more accurate when performing repro.

I have confirmed correct behavior on (no error icons shown on `about:blank` page) on Linux and Mac Canary 64.0.3248.0.  Could you please try the repro using `about:blank` on M63 ?

Verified the fix on Mac 10.12.6, Win-10 and Ubuntu 14.04 using Chrome version #63.0.3239.16 as per the comment #11.
Attaching screenshot for reference.
Did not observe any error/warning icons present in the top right, next to the 3-dot menu in dev tools.
Hence, the fix is working as expected. 
Adding the verified labels.

Thanks...!!

Deleted: 775239@Win-10.JPG 126 KB

	775239@Win-10.JPG 126 KB View Download

Thank for verifying!  Looks correct to me.