It worked on my Oppo Find 5 on 4.4.4 using the ART-Runtime - maybe it works on your device, maybe it won't
The Zip contains 2 files: LatinImeGoogle.apk and libjni_latinimegoogle.so
Place the apk in /system/app and the so in /system/lib and then go to Settings and set Google Keyboard as the standard Input Method. Then set go to the Keyboard's settings and click on Advanced Settings - there you can select the Material theme.
Here are the files:
Maybe I will create a flashable Zip tomorrow, but atm I don't have the time to do that-