So that's what it was.
I too thought there was something different, but unlike you it didn't bother me too much, I just went with the flow. Well spotted
@Sandman, all my Google created apps do close with the finger up and not down action, I've just checked. Hey even the link you supplied above to Google Navigation Drawer does the exact same thing through my mobile phone browser. When you press the burger menu button, the scrim reacts to finger up and not finger down, that's continuity for you.
Hmm, changing mBasePanel.TOUCH_ACTION_DOWN to
mBasePanel.TOUCH_ACTION_UP is what I probably would have done too if I had noticed it, but without trying it out for myself, I have absolutely no idea if TOUCH_ACTION_UP would work correctly. I have a strange feeling that it would cause an issue though.