Flutter P3: Performance metrics

We develop one flutter app we need focus to 06 metric performance below:

1. Startup time to the first frame: Check the time when WidgetsBinding.instance.firstFrameRasterized is true.

2. Frame buildDuration, rasterDuration, and totalSpan

3. Statistics of frame buildDuration (*_frame_build_time_millis): monitoring four stats: average, 90th percentile, 99th percentile, and worst frame build time.

4. Statistics of frame rasterDuration (*_frame_build_time_millis):  monitoring four stats: average, 90th percentile, 99th percentile, and worst frame build time.

5. CPU/GPU usage

6. Release_size_bytes to approximately measure the size of a Flutter app