Version: 49.0.2623.75 
OS: Ubuntu 12.04,14.04

What steps will reproduce the problem?
1.Launch Chrome-> Go to any Page(Ex:Chrome://Apps)
2.Now Press F12 to open Dev tools -> Go to Timeline section-> Now reload the page
3.Now at summary go to Event log -> Then move the "select the item for Details" window towards R.H.S(Please refer video) and observe unwanted scrollbar(Please refer screenshot)

Expected: Unwanted scroll bar should not be seen at Event log tab in Timeline section
Actual: Instead Unwanted scroll bar is seen 

Note : 1.Issue is not seen on Windows OS
2.Issue is reproducible on latest 51.0.2665.0 dev build

This is Regression Issue broken in M-49

Manual Good and Bad Builds are:
Good build: 49.0.2617.0
Bad build : 49.0.2618.0

Below is the Tool Bisect Info:

CHANGELOG URL:
https://chromium.googlesource.com/chromium/src/+log/7dd5420ff80dd39400e2639573005651b0c7961a..74b828cdf4026679cf1f85662f92093934b69800

Suspecting  https://codereview.chromium.org/1573673002 from changelog

@caseq : Please feel free to re-assign if its not related to your change
 

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