drawer broken on mobile safari

[timove]

The drawer panel of the paper-drawer-panel element cannot be swiped open if the swipe starts over content from the light dom. Swipes from shadow/shady dom content work as expected.

Expected outcome

Swiping with a finger from the left border to the right opens the drawer panel regardless of the origin of the content (light vs. shadow/shady dom).

Actual outcome

The drawer panel opens only a few pixels but not fully if the swipe starts over content from the light dom.

Steps to reproduce

1. Environment: iOS 9.1, Mobile Safari, page saved to home screen ("as app"), page started from home screen. Run on actual iPhone 6 device, not in simulator.
2. polyserve this project's fork: https://github.com/timove/paper-drawer-panel
3. Open http://machine:8080/components/paper-drawer-panel/test/iostest.html
4. Try to open the drawer by swiping from the red and green contents -- originating from light dom and shady/shadow dom respectively

[blasten]

this issue is confirmed. @azakus would you mind taking a look at this as well?

[blasten]

friendly ping @azakus. Something going on with event paths.