Chrome Version : 55.0.2855.0 (Official Build) 1f84049641ac0f80af74361acd0ea0df338479c4-refs/heads/master@{#417475} (32/64 bit)
OS: Mac(10.10.5)(10.11.5), Windows (7,8,8.1,10)

URL : www.gmail.com

What steps will reproduce the problem?
1. Launch chrome, navigate to above url and sign in to Gmail using valid credentials.
2. Open ‘hangouts contacts’ list, move the mouse cursor on any one of the ‘hangout contacts’ seen in list and click on ‘more options’(i.e iron icon) button.
3. Observe the delay while opening a ‘more options’ list.

Actual : Delay is seen while opening a ‘more options’ list for ‘Hangouts contacts’ on gmail.com
Expected : There should not be a delay while opening a ‘more options’ list for ‘Hangouts contacts’.

This is a regression issue broken in ‘M-55’, below is the Manual Regression and Narrow Bisect info. 
Good build: 55.0.2844.0
Bad build: 55.0.2845.0

Narrow Bisect : 
https://chromium.googlesource.com/chromium/src/+log/9da11463e3a843855f1d59ef6189c66e4b0e6ee2..84a3d0c455b12784c1fdee6dc8a3312380c9675c?pretty=fuller&n=10000

Suspecting: r415279 ? from Narrow Bisect

@wjmaclean : Please help to re-assign if your change is not the cause for this issue.

Note : Above issue is seen on Linux OS.
 

Deleted: Actual_delay.mov 5.2 MB

Actual_delay.mov 5.2 MB Download

Deleted: Expected_delay.mov 3.2 MB

Expected_delay.mov 3.2 MB Download