I have been using Windows for a while, and with it there is a feature when you want to upload a photo (for example) to a website, you click on the "Choose File" in Chrome to upload a photo, a "File Explorer" opens, and instead of selecting a file from the hard drive you can paste a URL into the "File Explorer" and press open and it will download the file from the web to your temporary files, and use it to be uploaded.

Is there any way I can do that in Ubuntu 12.10?

Here is the windows example:
Upload from url via File Explorer