Chrome Version:  51.0.2704.26
Chrome OS Version: 8172.12.0 
Chrome OS Platform: speedy, gandof, link, few other new devices
Network info: Ethernet(Both chromecast and chromebook are in same ethernet network, we are using ethernet to avoid network issue)

Please specify Cr-* of the system to which this bug/feature applies (add
the label below).

Steps To Reproduce:
(1) Copy MP4 video in Downloads
(2) Open video in HTML5 player
(3) Observe chromecast option in status bar
(4) choose chromecast device and do screencast

Expected Result:
Video should play smoothly in remote device like in chromebook.

Actual Result:
Video not playing smoothly, Repeatedly stopping for few seconds and playing again.

How frequently does this problem reproduce? (Always, sometimes, hard to
reproduce?)
Always

What is the impact to the user, and is there a workaround? If so, what is
it?

Please provide any additional information below. Attach a screen shot or
log if possible.
Cast is using default media-router option for cast, not chromecast extension.
Logs are added in next comment.