    Description: Add an item to the drag data store item list whose data is the string given by setData method's second argument

Test Result | Test Assertion
Manual | Test passes if if the word "PASS" appears to the left after following the steps below. Steps: Drag the blue image and drop it in the green box

http://dev.w3.org/html5/spec/dnd.html#datatransfer

If format equals "text", change it to "text/plain". Remove the item in the drag data store item list whose kind is Plain Unicode string and whose type string is equal to format, if there is one. Add an item to the drag data store item list whose kind is Plain Unicode string, whose type string is equal to format, and whose data is the string given by the method's second argument.