Currently every time we run src/tools/perf/generate_perf_data we run perf_data_generator.py that generates the list of becnhmark owners based on the tests specified in the chromium.perf.json file.  

Now that we are moving our benchmarks to be triggered on the bots (crbug.com/757933), chromium.perf.json will no longer specify each individual benchmark.  We need to move this generation away from the json file and instead generate it based on the benchmark_bot_maps in src/tools/perf/core