Add IODI2 support to symbolicator
Add IODI2 support to symbolicator

Summary: Support decoding layered metadata.

Reviewed By: newobj

Differential Revision: D23922849

fbshipit-source-id: c5f9dd5a18a6bd808ddb1316a9f9bd9a8596fa7a

facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex