Run individual scheduled tasks from web

1. Go to the scheduled tasks page EXPECTED: There should be a 'Run now' button (looks like a link) for all the tasks except the disabled ones. 2. Click the 'Run now' button for a scheduled task. EXPECTED: It should run the task, showing the same display as it would when it runs as part of normal cron. 3. Use this to run a long-running scheduled task, such as 'Update all installed language packs' or 'Legacy cron processing for plugins'. EXPECTED: While the task runs, you should see its output appear progressively (i.e. not all at once). [Note: If your system is super fast it might be hard to tell...] 4. Open a second browser so that you have two user sessions. Get both browsers in a position to run the same (long-running) scheduled task. Run the task very quickly from both browsers so that one is trying to start the task while the other is continuing it. EXPECTED: The task should run in the first browser, but in the second you should see the following debug information instead of of the task output: "Unable to get task lock for [task class] ." With regard to step 3 about showing progress during the task: a. It may be useful to check in multiple Moodle themes - the behaviour of 'clean' vs 'boost' is different, although I've got both working now I believe! b. There might be some browsers that won't display the page progressively even when we do output it progressively. I've confirmed that Chrome, Firefox, and Internet Explorer 11 running on Windows 7 all work for me, but I know we've seen problems in the past with some configurations.