I hope I'm submitting this feature request to the correct place, not quite sure.
Accessing the files attribute of an input element returns the files as FileList object, which is - AFAIK - part of the FileSystem API and therefore grants only read-only access to its contents.
Unfortunately there are several common use cases which would require the ability to programmatically _remove_ particular files from the FileList, which seems not to be possible currently.
a) Checking the file.size for some limit before uploading, if limit is exceeded exclude the particular file from uploading.
b) Giving the end-user an opportunity of reviewing his file selection and to exclude accidentally selected files.
Here's the discussion of a guy facing the same problem:
Mass move to "HTML WG"
This is not something for the HTML specification to change, FileList is defined by the File API specification (http://dev.w3.org/2006/webapi/FileAPI/#dfn-filelist).
But don't worry — I'm moving your bug there so that it can be processed by the right people, this is a good bug.
This bug is a likely dupe of Bug 17125.
Marking dupe. Let's continue discussion in Bug 17125
*** This bug has been marked as a duplicate of bug 17125 ***