Limit performance test duration

[clsid2]

It would be useful to have an option to limit the amount of frames that are decoded in each run during a performance test. For example 1000 frames. This would allow using files with long duration to test performance of the filter chain.

[mikecopperwhite]

If the graph supports setting a stop position with IMediaSeeking ( menu Play/Seek... ) seek the graph and set a stop position before starting the test. Each test run will stop at the stop position.

The performance test currently doesn't preserve the start position before testing starts. This would be a useful additional feature.