Version: 54.0.2816.0 5ca3397bac11535fb30249c96b9ee311fe2474a8-refs/heads/master@{#409090} (32/64-bit)
OS: Mac (10.10.5, 10.11.5)

What steps will reproduce the problem?
1) Launch chrome , navigate to www.google.com
2) Now open devtools and go to 'Timeline' section and record some activity
3) Now  click on 'Call Tree' option and drag the 'Call Tree' window downwards observe the 'Total time' and 'Activity' column borders

Actual : Column borders are seen misaligned after dragging the 'Call Tree' window downwards
Expected : Column borders should be seen properly

This is a non-regression issue, seen from M-48 series as 'Call Tree' option appears from build # 48.0.2555.0 

Kindly review the attached video and screenshot for reference.

Note : Issue is not seen on Linux and Windows OS.
 

Deleted: Actual_video.mov 1.5 MB

Actual_video.mov 1.5 MB Download

Deleted: Actual_screenshot.png 297 KB

	Actual_screenshot.png 297 KB View Download