Camera NX just updated to v7 which brings a lot of the Pixel 2 ‘exclusive’ features to your Nexus 5X/6P. The only thing that doesn’t work is Portrait Mode. HDR+ ZSL (zero shutter lag) and Motion pictures (Live photos) work. There are also additional options to ‘Show dirty lense warning’, HDR+ control, and to save the raw DNG files when taking HDR+ images in addition to the standard JPG.

To get it working, just install the app from the link below:
Camera NX v7

For non-Nexus devices you’ll need to install the version without ZSL:
Camera NX v7 NOZSL

Here’s the non-modded version of the Google Camera app:
Google Camera