What are the minimum requirements to charge the 2016 MacBook Pros? As the MacBook Pro 2016 series supports various USB PD profiles, I'm wondering whether they will also charge using other USB standards, for example:


USB Type-C, 1.5A or 3.0A at 5V using the passive marking resistor (not PD)
USB Type-A using an A to C cable, connected to a USB BC DCP at up to 1.5 A (for example newer iPhone or most Android compatible chargers)
USB Type-A, connected to an iPad charger at 2.1 A or 2.4 A (using Apple's proprietary D+/D- voltage handshake)


I'm aware that most of these will not be able to supply enough power for normal operation of the computer, but being able to charge slowly while in standby would still be useful.
After some experimentation with a 2016 15" MBP, it seems that they are very flexible:

A USB charger capable of 5 V, 2.4 A proprietary Apple signalling was recognized as providing 12 W of power, and an iPhone charger (which complies the USB BC specification) was shown as providing 5 W. The Nexus 5X charger, which provides USB-C 5 V, 3 A charging, was also correctly recognized as providing 15 W.

The power settings were showing these as "not charging" with the Mac running, but it turns out that even the large 15" MBP is capable of slowly charging from the tiny 5 V, 1 A adapter (it went up by about 2% after charging in sleep mode for about half an hour).