Jonah Williams 635a109a6d [Impeller] Add fence waiter trace event. (flutter/engine#43092) ...

I suspect that some of the worst frame times are caused by submission blocking on adding a fence. Add a trace event that would make that obvious.

![unnamed](https://github.com/flutter/engine/assets/8975114/93650ac8-4451-49d7-b8fa-00fc9f7f4277)

2023-06-22 17:17:48 +00:00

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src/flutter

[Impeller] Add fence waiter trace event. (flutter/engine#43092)

2023-06-22 17:17:48 +00:00