So after a few weeks of being without root on Android O for the Pixel user Sachi315 discovered how to get root on O by installing 7.1.2 on one slot and android O on the other. This allows Android O to fully boot after installing SuperSU. I wont go into the details of how it works because thus far its all speculation on my part and hopefully someone out there who knows more about these new partitions could better explain it. But for now I'm just going to show you how to do it.
+Download 7.1.2 for your Pixel (XL)
+Download Android O for your Pixel (XL)
+SuperSU RS4 2.79 Extra Delay
+TWRP RC1 bootable image & RC2 Flashable zip
-----For Pixel (https://dl.twrp.me/sailfish/)
-----For Pixel XL (https://dl.twrp.me/marlin/)
+Backup everything on you device, it will be purged
-----Make sure you have the latest fastboot binaries (I HIGHLY recomend you set this up manually. How to do so can be found in my tutorial here)
To make sure you have the latest fastboot binaries press the windows key and type cmd. In the command line type "fastboot" This should return you get. Showing all the available fastboot commands including the new "--slot" commands. If this list has the options --set-active[=<slot>], --slot <slot> listed towards the bottom then you're all ready to move on. (see screenshot for list of other commands you should see)
Editing the flash-all.bat from your downloaded 7.1.2 and android o factory images
-Extract both to your working folder
-Find the "flash-all.bat" in the extracted 7.1.2 (N2G47E) right click and select "Edit"
-At this point we are going to clean the flash all up a bit. Its not a necessity but if you don't add some much needed line breaks it can get messy and confusing.
-Below i have a screen shot of what mine looks like cleaned up. Just press enter in the places i did. *Adding the line breaks does NOT mess with the code at all*
-----Toward the end of the commands you will see i added '--skip-reboot" between "update" and "image-sailfish-n2g47e.zip" This command makes it to where the device will not restart after the flash-all is finished. It is important you add this in the same place.
-We are going to add a few "--slot" commands to it so it only installs to one slot. Below you can see what mine looks like after i added the commands. Match yours to mine (highlighted by red boxes)
-If you are on marlin, your image and zip names will be different but it's the same principal
Now we move over to the android o dev preview
-Open the extracted dev preview and right click on its flash-all.bat. Select "Edit"
-We are basically doing the exact same thing in this one BUT instead of the new commands being "slot _a" they will be "slot _b" (See below for the difference and we are still adding the "--skip-reboot" command)
Flashing the Images
Go ahead and get your Pixel into bootloader mode and plug it in.
before we start flashing we are going to clean the device up. This step will erase everything on the device.
Go into command prompt and type:
fastboot --slot _a -w
fastboot --slot _b -w
Let it do its thing and after its done, it should be left in bootloader.
now run the flash-all.bat from the 7.1.2 image folder you have.
Same thing; let it run its course and finish up.
Now you should be still in bootloader.
type in cmd
Installing TWRP and Root
From here; boot into TWRP (RC1)
-Make sure youre in slot A by going to "Reboot" then looking at the bottom (It should be slot A at this point, if its not something wasnt done correctly in the above steps)
+At this point i had the issue that my pixel would show up under "This PC" in explorer and was recognized by adb BUT none of the internal storage could be interacted with via my PC (this includes adb commands) so i couldnt get TWRP RC2 or SuperSU SR4 2.79 Extra Delay on the device to be flashed.
-To fix this: got to wipe>advanced wipe>check internal storage ONLY then wipe this partition.
-Unplug your phone and plug it back in and Windows Explorer should be able to work with the internal storage now.
-Now transfer TWRP RC2 and SuperSU sr4 2.79 Extra Delay to your Pixel
-From TWRP on your device, flash just TWRP RC2 for now. After it is installed, switch to slot b in TWRP. Then reboot to recovery.
-When TWRP comes back up, check to make sure youre in slot B still.
-If you are, now flash SuperSU SR4 2.79 Extra Delay.
-It should boot into android o, walk through setup and make sure supersu is installed.
-If it is, Congratulations you have rooted android O on your Pixel!
This method has was discovered by @Sachi315 (here)
Make sure you give him tons of thanks for getting the method up and running!