Forms do not prevent same data submission multiple times.

Go to any course. Turn editing on. Add a new activity, and select Forum type. Do not type in a name for the forum (this will cause client-side validation failure). Scroll down to the bottom and click one of the two Save buttons. EXPECTED: The validation error should show and the browser will probably scroll to it (well when I tried, to slightly below it, but that's a separate issue). If you scroll down to the bottom, the Save buttons are still enabled. Type in a name for the forum. Scroll down and click Save and return to course repeatedly, presing the mouse button as fast as you can. EXPECTED: You should probably see the button disable itself visibly before the page reloads. EXPECTED: When the page reloads (showing the course) you should see exactly 1 instance of the new forum. BEFORE FIX: Before this fix, it was usually possible to get 2 instances of the forum (sometimes more). Create another forum. This time, choose Save and display EXPECTED (no change): The new forum should display instead of the course page. (This is just testing it can still tell which submit button you clicked.)