am 6cfff14d: am efc1d15f: Merge "Reland "customtabs: Add "extraCommand" and "extraCallback", for unsupported commands"" into mnc-dev

* commit '6cfff14da52d678fad8f567d8525a6a4c2255c0b':
  Reland "customtabs: Add "extraCommand" and "extraCallback", for unsupported commands"