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

* commit 'efc1d15f9e5f77b87a079a6e3679de546e9fd39a':
  Reland "customtabs: Add "extraCommand" and "extraCallback", for unsupported commands"