composedPath() broken for tap event on touch devices

[Saulis]

Description

event.composedPath() is missing the composed elements within shadow root on tap event on touch devices. Native events and atleast down and up gesture events work as expected.

Looks to me like the problem is using a Touch object from e.changesTouches[0] as a sourceEvent instead of the original composed event.

Live Demo

http://jsbin.com/pagitax/edit?output

Steps to Reproduce

1. Tap on "Tap Me!"
2. See printed out composedPath() in console

Expected Results

Path should start with: ["DIV", "#document-fragment", "MY-ELEMENT", "BODY", "HTML"...]

Actual Results

Path actually starts with: ["MY-ELEMENT", "BODY", "HTML"...]

Verified with

• Chrome 58 emulating Nexus 5X
• Chrome 58 emulating iPhone 6
• iOS Simulator running iPad with iOS 10.3

Versions

• Polymer: v2.0.x
• webcomponents: v1.0.x

[dfreedm]

Yep, you're right. The right fix is probably to use the original TouchEvent in findOriginalTarget to get the proper composedPath