Update run_gtest_perf_test.py to streaming command output to stdout & log file at the same time

testing/scripts/run_gtest_perf_test.py

 #!/usr/bin/env python
 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Runs an isolated non-Telemetry perf test .
 
 The main contract is that the caller passes the arguments:
 
   --isolated-script-test-output=[FILENAME]
@@ skipping 84 matching lines @@
       if not '--test-launcher-print-test-stdio=always' in extra_flags:
         extra_flags.append('--test-launcher-print-test-stdio=always')
 
       if IsWindows():
         executable = '.\%s.exe' % executable
       else:
         executable = './%s' % executable
       with common.temporary_file() as tempfile_path:
         rc = common.run_command_with_output([executable] + extra_flags,
             env=env, stdoutfile=tempfile_path)
-        with open(tempfile_path) as f:
-          print f.read()
-
         # Now get the correct json format from the stdout to write to the
         # perf results file
         results_processor = (
             generate_legacy_perf_dashboard_json.LegacyResultsProcessor())
         charts = results_processor.GenerateJsonResults(tempfile_path)
         # Write the returned encoded json to a the charts output file
         with open(args.isolated_script_test_chartjson_output, 'w') as f:
           f.write(charts)
     except Exception:
       traceback.print_exc()
@@ skipping 24 matching lines @@
 if __name__ == '__main__':
   # Conform minimally to the protocol defined by ScriptTest.
   if 'compile_targets' in sys.argv:
     funcs = {
       'run': None,
       'compile_targets': main_compile_targets,
     }
     sys.exit(common.run_script(sys.argv[1:], funcs))
   sys.exit(main())