UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.18 Safari/537.36
Platform: 9982.0.2017_09_28_0645 (Test Build - pdswauto) developer-build squawks

Steps to reproduce the problem:
1. Create a simple benchmark similar to top_25_smooth (i.e. derived from the _Smoothness class), but with no scroll action (e.g., a falling leaves benchmark)
2. Run the benchmark and measure percentage_smooth
3. Smoothness measurements are inaccurate (very low)

What is the expected behavior?
In this example (falling leaves), Telemetry reports values as low as ~70% on platforms which are actually obtaining around 95% smooth frames.

What went wrong?
Telemetry is not picking up the DrmEventFlipComplete events (the preferred source of frame timing data) and instead falls back to less accurate sources of data (i.e., BenchmarkInstrumentation::*RenderingStats) for measuring frame times.

Did this work before? N/A 

Chrome version: 63.0.3226.0  Channel: dev
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Flash Version: