Handling payload
Handling payload

Summary:
- Added `treeNodeIndexPath` to `FocusInfo` which represents the path to the selected node in the component tree.
- Extracting scope root ID from payload to identify the time line track that corresponds to the selected component.
- Finding the most recent 'Tree Build' event on the track so we can be sure the selected component is in the associated component tree.
- Extracting the index path to the selected node in the tree.

Reviewed By: kevin0571

Differential Revision: D23160875

fbshipit-source-id: 8607bf7b34bca1374f9fafded197b35c811f3f75

facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper