Bug 970777 - Remove redundant |numLoaded| checks in dom/browser-element/mochitests/*.js. r=smaug

1. Make the test more solid
2. Postpone the second |takeScreenshot| right after the |iframe1| is onload again
3. Remove redundant |numLoaded| by assigning |iframe1.src| first.
BUG 914031: Added menclose notation phasorangle and Reftest. r=fredw.
Bug 1004669 - Fix leaks in MediaTaskQueue::Dispatch(). r=cpearce