UserAgent: Mozilla/5.0 (X11; CrOS x86_64 9334.72.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.140 Safari/537.36
Platform: 9334.72.0 (Official Build) stable-channel guado

Steps to reproduce the problem:
1. open app "files"
2.click on a file with .php extension
3. should offer caret or open caret

What is the expected behavior?
should offer caret or open caret, since it is registered for any text file

What went wrong?
app "files" cannot open the .php file.

WebStore page: the files app (default installed and included in chrome os) and caret https://chrome.google.com/webstore/detail/caret/fljalecfjciodhpcledpamjachpmelml

Did this work before? N/A 

Chrome version: 58.0.3029.140  Channel: stable
OS Version: 9334.72.0
Flash Version: Shockwave Flash 25.0 r0

See also: https://github.com/thomaswilburn/Caret/issues/577