Chrome Version: 61.0.3163.123
Chrome OS Version: 9765.85.0
Chrome OS Platform: Asus C202S
Network info: Irrelevant to this defect

Steps To Reproduce:

1. Attach a USB MTP device that presents multiple files and will synthesize an error condition for one of said files when it is retrieved.
2. Select multiple files from the attached device in the Chrome OS Files application, right-click, and select "Copy."
3. Navigate in the Files application to a folder on the local device or on Google Drive.
4. Right-click and select "Paste."
5. When the batch copy operation gets to the file for which the USB MTP device synthesizes an error, observe the inadequate error notification that appears in the lower-left corner of the Files window.


Expected Result:

An error notification naming the file that was not copied successfully.


Actual Result:

An error notification that does not name the file involved in the error condition.


How frequently does this problem reproduce?

Always.


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

When one or more files in a batch copy operation fail to copy, the user must choose between manually checking every file that they attempted to copy to ensure that it copied successfully or assuming that any one of the files they attempted to copy could be corrupted or missing on the target storage.  This frustrates the user.


Narrative:

If an error is encountered on a single file while copying multiple files in a batch over MTP, the Chrome OS Files application displays an error notification that is clearly worded for a context in which only a single file is copied and that omits the name of the file to which the notification applies.  (The notification reads: "Copy operation failed.  The file or the directory is not usable.")  This requires the user to manually check every file that they attempted to copy in the batch or to assume that any one or more of the files they attempted to copy did not copy correctly.

When copying multiple files over MTP, the Chrome OS Files application should display errors that are worded appropriately for a multi-file batch context and should name explicitly the affected files.

(I did not test other transport methods besides MTP, but it's reasonable to expect they may also be affected.)