cocos2d/cocos2d-x — pull request #6842 by minggo (2014-05-20 08:39:13+00:00)
Title: don't have to compare in step since it is done in init function

In `ActionInterval::initWithDuration()`, there is codes
```cpp
// prevent division by 0
// This comparison could be in step:, but it might decrease the performance
// by 3% in heavy based action games.
if (_duration == 0)
{
_duration = FLT_EPSILON;
}
```

But it also compares in `ActionInterval::step()` too.