Version: 55.0.2861.0 9cedf75377d817c6b32a01f1d30fbe10663b8bb8-refs/heads/master@{#418732} (64-bit)
OS: Windows (7,8,8.1,10),Linux (14.04 LTS),Mac OS X(10.10.5, 10.11.4)

What steps will reproduce the problem?
1. Launch chrome and navigate to chrome://md-settings/searchEngines
2. Now scroll down the page and observe the header part and search box on the page

Actual: Weird overlapping of 'Manage search engine' overlay is seen with search box when page is scrolled down
Expected: Weird overlapping of 'Manage search engine' overlay should not be seen with search box when page is scrolled down

This is regression issue, broken in ‘M 55’ and below is manual regression and narrow bisect info:
Good build : 55.0.2844.0
Bad build : 55.0.2845.0

Narrow Bisect info : 
https://chromium.googlesource.com/chromium/src/+log/8bbaf67cd3ac821e9389dd3c9f02f74980b17eac..3fdd34c518ece6d426cb559b71f84289a1027f31?pretty=fuller&n=1000

Suspecting: r415443 from Narrow bisect

@dschuyler : Could you please help to reassign if your change is not the cause for this change.

 

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