(These are specified as { font-family: Roboto; font-weight: 500; } which according to comments on that CL should have continued to work.)

Medium(500) cannot be much stronger than Regular/Normal (400).  They're just a step apart. 'Medium' being barely bolder than 'Regular' is arguably the way they're supposed to be. 

By 'Google Font Demo', you mean 'specimen test page' at google.com/fonts?  Hmm, https://fonts.google.com/specimen/Roboto?query=Roboto&selection.family=Roboto indeed shows a great constrast between Regular and Medium. 

There are two possible causes for the perceived weight differences:

1) When any font is used as a web font, it's always auto-hinted by Chrome (on Chrome OS/Linux via FreeType. Roboto bundled in Chrome OS as local fonts, otoh, is NOT auto-hinted but relies on built-in byte codes. Hinting difference can lead to a difference in perceived weight (espeically on low res devices). 

2) The weight of Medium has changed somehow between versions. Google Web Font is currently serving a rather old version ( > 1 year old) and that's what used to be bundled as resources (before I removed them). What's included as local system fonts is newer (2.132). 

If it's #1, I can change the way Roboto is hinted on CrOS. 

Neither is very likely, though. I'll take a look. 

Where should I look for in chrome://history? I inspected a few button(-like elements) in the page (after enabling MD for history and restarting), but all of them are styled with 'font-weight: normal'. 

Hmm, my Chromebook is still in 54.0.2824.0 dev, but that version contains Roboto-dropping CL ( https://chromium.googlesource.com/chromium/src/+log/54.0.2817.0..54.0.2824.0?pretty=fuller&n=10000 ). 

I found a paper button in chrome://download. 

data:text/html,<span style="font-family: Roboto; font-weight: 700; font-size:13px;">Open Download</span><br><span style="font-family: Roboto; font-weight: 500; font-size: 13px;">Open Download</span><br><span style="font-family: Roboto; font-weight:400; font-size: 13px;">Open Download</span>

ANyway, attached is the screenshot of the above data url. 
From the top, the weight is 700, 500 and 400. 

The second and the third do have quite a large contrast (similar to what I see at  https://fonts.google.com/specimen/Roboto?query=Roboto&selection.family=Roboto

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Two screenshots attached below are:

1. Both 'Clear All' and 'Open Download Folder' are styled with 'Roboto @500, 13px'

2. 'Clear All' is styled with 'Roboto @400, 13px' while 'Open Download Folder' is left alone. 

In the second screenshot, there is an enough weight difference to me. If it's too small for you, I think you'd better use 'weight=700'. 

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To see  if either of two possibilities in comment 2 led to the perceived weight difference, I'll also set up a test page. 

Changing the summary... because 'Roboto Medium' IS available/accessible on Chrome OS. 

> To see  if either of two possibilities in comment 2 led to the perceived weight 
> difference, I'll also set up a test page. 

Well, actually to my eyes, the weight contrast in the 2nd screenshot in comment 5 is comparable to that at https://fonts.google.com/specimen/Roboto?query=Roboto&selection.family=Roboto.  (well, the size is different, etc so that there are some skewing factors let alone individual difference/screen resolution/ etc). 

So, I'm not sure if there's an issue here. 

http://jungshik.github.io/cr/bugs/638393/ compares 3 different ways of using Roboto:

1. Roboto 2.132 as included on Chrome OS as local system fonts: FreeType BCI hints used
2. Roboto 2.132 as web fonts: FreeType Light Auto Hint 
3. Roboto old (as served by Google Web Font): FreeType Light Auto Hint

#3 is the same as what bundling Roboto (old from GWF) as resources did. 

Attached is a screenshot taken on Pixel with 54.0.2831.0 (canary). 
I don't see any noticeable difference in weight contrasts among three columns. 

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Attached is a screenshot taken on a low res Chromebook (the same test page as mentioned in comment 9).   

At low res ( ~120 dpi), hinting makes a difference in Roboto Thin (100). However, I don't seen any noticeable difference in the weight contrast between Regular/Normal (400) and Medium (500) in all three columns. 

Based on these results, I'm closing this bug. 

michaelpg@: 
Let me know if there's anything you think we need to do. 
                                                 

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BTW, the screenshot in comment 10 was taken with 54.0.2830.0 (my own build). 

I will take another look and report back with screenshots. My recollection was that the before/after of that CL caused a clear difference in appearance on CrOS, with font-weight: 500 going from "mostly bold" to "mostly normal".

FWIW, on Windows and Linux the 500-weight Material buttons still look bold-ish to me, a stark difference from the same Chrome version on samus where they look like the "Regular" from jshin's sceenshots.

IMHO, medium is not supposed to be bold-ish. 
Note also that how bold it looks depends on a number of factors (resolution, font size, color as well as rasterization method). 

OK, everything looks fine now on my Pixels (54.0.2830.0, 54.0.2833.0) and another Chromebook.

font-weight: 500 no longer looks super skinny, and is clearly differentiated from 400.

Unless there's some wonky requirements for repro, I must have screwed something up in my investigation. ¯\_(ツ)_/¯

Thanks for checking on this, even if it was just my imagination.

Good to hear that everything is fine. Thank you for confirming !