UserAgent: Mozilla/5.0 (X11; CrOS armv7l 10718.58.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.70 Safari/537.36
Platform: 10718.58.0 (Official Build) beta-channel veyron_minnie

Steps to reproduce the problem:
I created an app that captures desktop images and uses those in NaCl module.
The app gets a desktop stream by using navigator.webkitGetUserMedia, posts it to NaCl,
and gets each frame data by using OnGetFrame in NaCl().
Problem is reduction of OnGetFrame's FPS.
When a user does nothing, OnGetFrame is called rarely(every 20 seconds).

I attached an app that logs when OnGetFrame is called. Please use it below steps.
1.(Preparation) Connect to External Display.
2. Launch the app and choose Internal Display.
3. Show Console window by using inspector.
4. Hide the app window, move inspector window to external display, and move mouse cursor to external display.
(Step 4 makes "User does nothing" environment.)
5. Check OnGetFrame call by log.

What is the expected behavior?
OnGetFrame is called frequently(every 50 ms).
(Stable:67.0.3396.99 is good response)

What went wrong?
OnGetFrame is called rarely(every 20 seconds).
(Beta:68.0.3440.70 is rarely response)

WebStore page: 

Did this work before? Yes Stable:67.0.3396.99

Chrome version: 68.0.3440.70  Channel: beta
OS Version: 10718.58.0
Flash Version: 30.0.0.134 /opt/google/chrome/pepper/libpepflashplayer.so

Attathed sample app is based on nacl_sdk/pepper_49/examples/api/media_stream_video.
I added navigator.webkitGetUserMedia in moduleDidLoad and LogToConsole in OnGetFrame.
 

Deleted: media_stream_video_desktopcapture.zip 2.8 MB

media_stream_video_desktopcapture.zip 2.8 MB Download