3764: Diff upload bug on Firefox with special file names

maxime*******@smil**** (Google Code) (Is this you? Claim this profile.)
What version are you running?

What's the URL of the page containing the problem?

What steps will reproduce the problem?
1. Use Firefox
2. Select a diff file (with a "special" name, see below) to upload
3. Fill in a base directory
4. Submit

What is the expected output? What do you see instead?
Expected: diff file uploaded
Seen: No upload and "Unknown error" message

What operating system are you using? What browser?
Linux / Firefox 35

Please provide any additional information below.
The problem occurs on Firefox (not on Chrome).
On Firefox, no HTTP request is sent (seen on Firebug network tab): the error occurs before the ajax call.
The file name (in our test: "Anomalie_#331845__[inbound]_–_[TNF]_–[Return_confirmation_email]_-_Formatting.patch") seems to be the problem.

After some JS debugging, I've discovered in the "_onValidateError" function that xhr.statusText="InvalidCharacterError: String contains an invalid character".
I suspect one of the special characters of the file name to be the problem.
The solution should be to sanitize the file name before the ajax call.