This is the keyboard from The Android L Dev Preview (Primary release for app devs to optimize apps according to it)
It was shared by @bejunk in this thread
Go above if u need support or anything......
Heres a direct link from the above thread..
Download And Flash By CWM (Didnt test thru cwm coz manual was faster)
Or Manually Install it by pushing the apk in /system/app/
and the lib in /system/lib/ with the proper permissions (i use mi file explorer and it sets permission on its own)
(if u have older version of google keyboard make sure to uninstall it first)
Now to get the keyboard working with the theme as shown in the preview..
-Go to Keyboard Settings
-Go to Advanced (Expert) Settings
-On Color scheme CHOOSE ''Material''