Fixes bug where stroke becomes very thin and strokes are sometimes ignored completely depending on event timing.

Fixes bug where stroke becomes very thin and strokes are sometimes ignored completely depending on event timing. This occurred on at least Chrome.

![image](https://f.cloud.github.com/assets/1131906/1581915/37d3f3f6-51e2-11e3-9986-891152f3aa8c.png)

Note to self: Next time remember to create a new branch, even for a one-liner.