[try] use same parser options in AST tab as typechecking tab
[try] use same parser options in AST tab as typechecking tab

Summary:
the "Errors" and "JSON" tabs come from typechecking, where we have all the experimental features turned on. the "AST" tab comes from calling `parse(content, {})`. since it didn't pass any options (`{}`), the experimental features would error in that tab but not the others.

ideally this would be configurable and affect both typechecking and parsing.

fixes https://github.com/facebook/flow/issues/5672

Reviewed By: calebmer

Differential Revision: D6751104

fbshipit-source-id: 8254507f2147ead6879610ff3795f16c33470827

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