Do not recompute the title of Net async slice if it is redrawn
Merge pull request #646 from xunjieli/netAsyncSliceDoNotRecompute

Do not recompute the title of Net async slice if it is redrawn
Use source type as title for top level events
Merge pull request #649 from xunjieli/source_type_as_title

Use source type as the title for top level events