Example usage:
$ tools/perf/run_measurement --browser=release \
--output-format=csv --output=/path/to/loading_measurement_output.csv \
- loading_measurement tools/perf/page_sets/top_1m.json
+ loading_measurement tools/perf/page_sets/top_1m.py
$ tools/perf/measurements/loading_measurement_analyzer.py \
--num-slowest-urls=100 --rank-csv-file=/path/to/top-1m.csv \
/path/to/loading_measurement_output.csv