Chrome Version : 54.0.2836.0 (Official Build) 5916d5e380c5a9da48673de99d40267507d46f34-refs/heads/master@{#413363} (64-bit)
OS: Mac(10.10.5)(10.11.5)

URL : https://chrome.google.com/webstore/detail/true-colors/fnafckfchfclgjlgjphdgajpnleoedce?hl=en

What steps will reproduce the problem?
1. Launch chrome, navigate to above url and click on ‘Add to chrome’ button.
2. Immediately switch to incognito mode and wait until info bar appears.
3. Observe the ‘Undo’ button on info bar. 

Actual : ‘Undo’ button on info bar is seen in bold font.
Expected : ‘Undo’ button should be seen in regular font.

This is a regression issue broken in M-51, below is the Manual Regression and Narrow Bisect info.
Good build: 51.0.2663.0
Bad build: 51.0.2664.0

Narrow Bisect : 
https://chromium.googlesource.com/chromium/src/+log/5121a34129f274edc61a288f73f99b39eb06e1e7..b38be38cee2027dcb827ebc61abb23508b8e5d25?pretty=fuller&n=10000

Suspecting: r378367 ? from narrow bisect.

Note : 
1. This is Mac specific issue and not seen on Windows and Linux OS.
2. Above issue is seen for all the themes available in chrome web store.
 

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