Example URL:
https://r6---sn-q4fl6n7e.googlevideo.com/videoplayback?id=aa9442b345c88696&itag=22&source=picasa&begin=0&requiressl=yes&pl=14&sc=yes&mime=video/mp4&lmt=1487180234241332&ip=73.74.27.27&ipbits=8&expire=1488026742&sparams=expire,id,ip,ipbits,itag,lmt,mime,mm,mn,ms,mv,pl,requiressl,sc,source&signature=34565499E3C010CFB3AE8B7ECAA46FE8EFB23CD7.664E2632B85E600348490F2EB8B69CFB778D1126&key=cms1&cpn=Gen1yHm1sfwKNtZt&c=WEB&cver=1.20170222&redirect_counter=1&cm2rm=sn-vgqz77l&req_id=8b3786a523d4a3ee&cms_redirect=yes&mm=39&mn=sn-q4fl6n7e&ms=ltr&mt=1487997843&mv=m

Steps to reproduce the problem:
1. Open the included link in Chrome for Android
2. Observe that even though it is playing an mp4 in Chrome's native player, the chromecast button is absent.
3. 

What is the expected behavior?
The expected behavior is to have the chromecast button present and functional.

On the other hand, streaming from other sources works:
http://download.blender.org/peach/bigbuckbunny_movies/

my gut feeling is that the cast button only shows up if the URL has a file extension (example: https://*.mp4)

Chrome should check the filetype using a method that doesn't rely on detecting file-extensions.

What went wrong?
Chromecast button is not available for native html5 videos where the filename/extension is obscured. The button is available for videos where the URL contains the filename/file-extension.

Did this work before? N/A 

Is it a problem with Flash or HTML5? HTML5

Does this work in other browsers? N/A

Chrome version: 56.0.2924.87  Channel: stable
OS Version: 7.1.1
Flash Version: Shockwave Flash 24.0 r0

Contents of chrome://gpu: