UserAgent: Mozilla/5.0 (X11; CrOS x86_64 7834.60.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.95 Safari/537.36
Platform: 7834.60.0 (Official Build) stable-channel kip

Steps to reproduce the problem:
We are running into the same problem that is documented in  Issue 471907 , where we cannot install a specific app in a public session.  In the comments for this issue, you state: "If you have a use case that you would like to solve with Chrome OS but can't, please open a new bug and provide full details on what it is that you're trying to achieve so we can consider what an appropriate solution would be."  

We are a public library that is teaching Arduino development.  We would like to take advantage of the Public Session feature for our public computers running Chrome OS.  Since we want to allow Arduino development on any  public computer, we would like to install the Codebender App (magknjdfniglanojbpadmpjlglepnlko) in the public session.  However, when we do, we get, "blah extension id is not allowed in this type of session".

What is the expected behavior?
We should be able to install Codebender and other useful packaged apps so that we have a fully functional public session, similar to our Windows machines, which feature the Arduino IDE.

What went wrong?
Certain apps (notably Codebender App) are blocked from being installed in a public session.  This forces us to enable sign-ins from other accounts (which will not be subjected to the time limit features that a Public Session has) and forces the user to create/use a personal Google account.

Did this work before? No 

Chrome version: 49.0.2623.95  Channel: stable
OS Version: 7834.60.0
Flash Version: Shockwave Flash 21.0 r0

Thank you for reading this report.  Please let me know if there are things that need to be clarified.