Chrome use-mobile-user-agent not working

The string is built to "Chrome/53.0.2785.116 Mobile" in GetShellUserAgent, then in BuildUserAgentFromProduct, product is not used, and passed on to BuildUserAgentFromOSAndProduct, which is supposed to format a string as such;

"Mozilla/5.0 (%s) AppleWebKit/%d.%d (KHTML, like Gecko) %s Safari/%d.%d"

The product string is inserted into token four, where the fourth replacement token is before "Safari". Therefore "Chrome/53.0.2785.116 Mobile" should be placed there.

With and without the flag, my user agent is the same.

Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.116 Safari/537.36

So what does this mean, is it broken? Quite possibly.

In src/extensions/shell/common/shell_content_client.cc, BuildUserAgentFromProduct("Chrome/" PRODUCT_VERSION) is called in ShellContentClient::GetUserAgent. That just circumvents the call to GetShellUserAgent.

Well. There goes the mobile user agent flag. There's other places it's possible for the product to be replaced, but that's the one that sticks out as the culprit.