Re: [PATCH v5 0/2] MR7833: mf: Update state and start clock for both paused and stopped.

[Brendan McGrath (＠redmcg)]

> Is this an artifact of your tracing or OnClockRestart() is actually never used?

It was calling `OnClockStart`, but it turns out that was because I had hard-coded the value in my `MESourceStarted` and `MEStreamStarted` events. After changing these events to instead use `pvarStartPosition` passed in `IMFMediaSource::Start`, I get:
```
1330.024952|10088|source_mock_Start: format: {00000000-0000-0000-0000-000000000000} (GUID_NULL) position: <EMPTY>
1330.025598|10088|clock_sink_OnClockRestart: system time 13300255028
```

So sending those events with a hard-coded `VT_I8` value of zero caused `OnClockStart` to be called, but now those events have a value of `VT_EMPTY` and `OnClockRestart` is called.