Unable to provide bisect using per-revision script,hence bisected with old script: 

Narrow Bisect info : 

You are probably looking for a change made after 565481 (known good), but no later than 565490 (first known bad).

CHANGELOG URL:

The script might not always return single CL as suspect as some perf builds might get missing due to failure.
  
https://chromium.googlesource.com/chromium/src/+log/172be4b9edff0ef700e1b57d11452f331d9ba0bf..8f2f9568808ee117698e0a9008a0b52902d2363e?pretty=fuller&n=10000

Suspect: https://chromium.googlesource.com/chromium/src/+/8f2f9568808ee117698e0a9008a0b52902d2363e

@erikchen: Could you please check whether this is caused with respect to your change, if not please help us in assigning it to the right owner.

Note:
(1) Above issue is reproducible only on Mac(10.12.6, 10.13.1, 10.13.6) OS and not seen on not seen on Windows(7,8,8.1,10) and Linux(14.04) OS.
(2) On Pressing Cmd+C , observe that unnecessary devtools window gets opened.

Thank You!

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Adding release blocker label for this issue.Please reduce priority or remove if not the case.

Thank You!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/315d4286bf50511d859f1c4f205966f4bccc5c22

commit 315d4286bf50511d859f1c4f205966f4bccc5c22
Author: Erik Chen <erikchen@chromium.org>
Date: Fri Jun 08 20:50:42 2018

Change IDC_DEV_TOOLS_INSPECT to use virtual keycode on macOS.

The mapping was added in https://codereview.chromium.org/3011002. There was no
reason for it to use a character rather than a virtual keycode.

After a recent refactor, this logic caused cmd + c to trigger
IDC_DEV_TOOLS_INSPECT, since the shift key is ignored for character comparisons.

Bug:  846893 ,  850895 
Change-Id: Ic74e418bd9fa55eda90dd3bd55b10a456abce581
Reviewed-on: https://chromium-review.googlesource.com/1093301
Commit-Queue: Erik Chen <erikchen@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565735}
[modify] https://crrev.com/315d4286bf50511d859f1c4f205966f4bccc5c22/chrome/browser/global_keyboard_shortcuts_mac.mm

 Issue 851257  has been merged into this issue.

(Still broken after #565735; not sure if that's expected.)

The dupe reports that cmd-shift-n for incognito isn't working either.

Based on the duplicate  Issue 851257  and C#9, marking this RB-Dev for tracking purpose.

 Issue 851353  has been merged into this issue.

 Issue 851354  has been merged into this issue.

 Issue 851443  has been merged into this issue.

 Issue 851560  has been merged into this issue.

Issue 851557 has been merged into this issue.

 Issue 851624  has been merged into this issue.

Ok it fixed the Cmd-C issue. 
But the underlying issue was not fixed.

same issue still occurs with at least these two shortcuts:
Cmd-Shift-T
Cmd-Shift-N

That fix recently landed [just missed this Canary]. It will be present in the next Canary: https://bugs.chromium.org/p/chromium/issues/detail?id=851259#c7

 Issue 851672  has been merged into this issue.

Update :
Rechecked the above issue on Mac(10.12.6, 10.13.1, 10.13.6) with latest Canary Chrome version #69.0.3455.0 and the issue is fixed.

Kindly refer the attached screen cast.

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The latest build has fixed the copy paste but Cmd-Shift-T Cmd-Shift-N are still busted.

Using the menu version of them works just fine.

Left and Right arrow keys doesn't in text fields doesn't work.
Same issue with Page Up + Page Down.

In any textfield with some text, Press and Hold left/right arrow key, cursor only moves one character and then stops. Need to tap the arrows keys one by one for each character. Similarly In any long webpage Press and Hold PageDown. Only one page is scrolled and then scroll doesn't work.

Arrow key lag has been reported in 851260

https://bugs.chromium.org/p/chromium/issues/detail?id=851260

 Issue 853878  has been merged into this issue.

Issue 851597 has been merged into this issue.

Issue 851602 has been merged into this issue.