Extend run-benchmark script to support human-readable results conversion.

Extend run-benchmark script to support human-readable results conversion.
https://bugs.webkit.org/show_bug.cgi?id=149944

Reviewed by Ryosuke Niwa.

Add '--read-results-json' and '--no-adjust-unit' options.
'--read-results-json' option converts result file to human readable format.
'--no-adjust-unit' option skips scientific notation convertion.
'--platform' defaults to 'osx' and '--browser' defaults to 'safari'.

* Scripts/webkitpy/benchmark_runner/benchmark_results.py:
(BenchmarkResults.format):
(BenchmarkResults._format_tests):
(BenchmarkResults._format_values):
* Scripts/webkitpy/benchmark_runner/benchmark_runner.py:
(BenchmarkRunner.__init__):
(BenchmarkRunner._run_benchmark):
(BenchmarkRunner._dump):
(BenchmarkRunner.show_results):
(BenchmarkRunner._show_results): Deleted.
* Scripts/webkitpy/benchmark_runner/run_benchmark.py:
(parse_args):
(start):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@190779 268f45cc-cd09-0410-ab3c-d52691b4dbfc