The "Browse Files' and "Add More Files' buttons aren't activated by the keyboard.

Steps to reproduce:

1) Open the inline version of uploader from the daily build site:
http://build.fluidproject.org/fluid/sample-code/uploader/inline/index.html

2) Click 'Add Files'

3) Using the keyboard tap the 'tab' key until the "Browse Files" button has focus.

4) Using the keyboard tap the 'enter' key. Notice that the File Open dialog does not open

5) Using the mouse click the "Browse Files" button and add some files

6) Tap the 'tab' key and then "Shift Tab' to put focus on the "Add More" button

7) Using the keyboard tap the 'enter' key. Notice that the File Open dialog does not open/