Using a USB HID sensor I can only seem to enumerate the device with the chrome.usb API on ChromeOS.
On OS X I can enumerate with the chrome.hid API with no problem.
What could be the reasons for HID devices not being identified as such on ChromeOS?
It is possible the device is blacklisted by the Linux HID driver. If you can put your Chrome OS device in developer mode or connect the device to a Linux computer you can check the kernel log to see how the device is recognized. If all is well then there should be a /dev/hidraw node created for the device.
Can you tell me what the device vendor and product IDs are?