global leaks improvements

[fool2fish]

3 improvements

1. in ie6,7,8 and opera, insert iframe will cause global leaks

analysis

An iframe could be approached by window[iframeIndex].
In ie6,7,8 and opera, iframeIndex is enumerable, this could cause leaks.

solution

see: lib/runner.js 540

2. in firefox, window.getInterface may cause global leaks

analysis

If runner runs in an iframe, this iframe's window.getInterface method not init at first.
It is assigned in some seconds.

solution

see: lib/runner.js line536

3. in some browsers, mocha.globals([...]) make tests run very slow

analysis

• if user specified globals argument, every time a test finished, filterLeaks() will run.
• nested loop is not efficient

solution

• see: lib/runner.js line164 ~ 165. I use this.prevGlobalsLength to remember how many global variables are when last test finished. When this test finished, this.prevGlobalsLength will be compared with globals.length, if they are equals, I think this test dose not has global leaks, so filterLeaks() could be jumped.（it is not very strict, if someone delete a global variable, and then create a new one in this test, this won't be found. but if it happened, just let it go). this promotion is huge.
• see: lib/runner.js line531 ~ 547. I moved some code to outer loop from inner loop. this cuts down run time by 50%.

[lepture]

ping ...