Implement OpaqueType
Implement OpaqueType

Summary: Implements the walker for OpaqueType

Reviewed By: pieterv

Differential Revision: D6358250

fbshipit-source-id: 74b68528c1d4d55d4f7d3cc2620e9aa057fb0995

facebook/flow,gabelevi/flow,jamesgpearce/flow,popham/flow,jamesgpearce/flow,nmote/flow,nmote/flow,popham/flow,AgentME/flow,gabelevi/flow,gabelevi/flow,mroch/flow,samwgoldman/flow,facebook/flow,samwgoldman/flow,mroch/flow,facebook/flow,mroch/flow,samwgoldman/flow,jamesgpearce/flow,popham/flow,nmote/flow,jamesgpearce/flow,facebook/flow,claudiopro/flow,gabelevi/flow,AgentME/flow,AgentME/flow,JonathanUsername/flow,claudiopro/flow,jamesgpearce/flow,jamesgpearce/flow,JonathanUsername/flow,AgentME/flow,gabelevi/flow,gabelevi/flow,samwgoldman/flow,popham/flow,AgentME/flow,JonathanUsername/flow,samwgoldman/flow,facebook/flow,claudiopro/flow,nmote/flow,samwgoldman/flow,samwgoldman/flow,popham/flow,mroch/flow,nmote/flow,facebook/flow,popham/flow,mroch/flow,claudiopro/flow,JonathanUsername/flow,claudiopro/flow,jamesgpearce/flow,gabelevi/flow,mroch/flow,JonathanUsername/flow,JonathanUsername/flow,popham/flow,nmote/flow,JonathanUsername/flow,nmote/flow,facebook/flow,mroch/flow