Setting --run-python-script flag for runtest.py invocation.

scripts/slave/recipes/chromium.expected/full_tryserver_chromium_perf_win64_nv_tester.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[build::bisect_tester]\\resources\\put_temp.py"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "saving url to temp file",
     "stdin": "http://build.chromium.org/p/tryserver.chromium.perf/json/builders/win64_nv_tester/builds/571",
@@ skipping 294 matching lines @@
       "--target",
       "Release_x64",
       "--factory-properties",
       "{\"bisect_config\": {\"bad_revision\": \"300148\", \"bug_id\": \"425582\", \"builder_host\": \"master4.golo.chromium.org\", \"builder_port\": \"8341\", \"command\": \"tools/perf/run_benchmark -v --browser=release page_cycler.intl_ar_fa_he\", \"good_revision\": \"300138\", \"gs_bucket\": \"chrome-perf\", \"max_time_minutes\": \"5\", \"metric\": \"warm_times/page_load_time\", \"repeat_count\": \"2\", \"test_type\": \"perf\", \"truncate_percent\": \"25\"}, \"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"build_data_dir\": \"[ROOT]\\\\build_data_dir\", \"buildername\": \"win64_nv_tester\", \"buildnumber\": 571, \"job_name\": \"f7a7b4135624439cbd27fdd5133d74ec\", \"mastername\": \"tryserver.chromium.perf\", \"parent_build_archive_url\": \"gs://test-domain/test-archive.zip\", \"parent_buildername\": \"Win x64 Builder\", \"parent_got_revision\": \"1111111\", \"recipe\": \"chromium\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}",
       "--build-properties",
       "{\"bisect_config\": {\"bad_revision\": \"300148\", \"bug_id\": \"425582\", \"builder_host\": \"master4.golo.chromium.org\", \"builder_port\": \"8341\", \"command\": \"tools/perf/run_benchmark -v --browser=release page_cycler.intl_ar_fa_he\", \"good_revision\": \"300138\", \"gs_bucket\": \"chrome-perf\", \"max_time_minutes\": \"5\", \"metric\": \"warm_times/page_load_time\", \"repeat_count\": \"2\", \"test_type\": \"perf\", \"truncate_percent\": \"25\"}, \"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"build_data_dir\": \"[ROOT]\\\\build_data_dir\", \"buildername\": \"win64_nv_tester\", \"buildnumber\": 571, \"job_name\": \"f7a7b4135624439cbd27fdd5133d74ec\", \"mastername\": \"tryserver.chromium.perf\", \"parent_build_archive_url\": \"gs://test-domain/test-archive.zip\", \"parent_buildername\": \"Win x64 Builder\", \"parent_got_revision\": \"1111111\", \"recipe\": \"chromium\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}",
       "--step-name=Performance Test 1 of 2",
       "--builder-name=win64_nv_tester",
       "--slave-name=TestSlavename",
       "--build-number=571",
-      "tools/perf/run_benchmark.exe",
+      "--run-python-script",
+      "tools/perf/run_benchmark",
       "-v",
       "--browser=release",
       "page_cycler.intl_ar_fa_he"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "Performance Test 1 of 2",
     "stderr": "/path/to/tmp/",
     "stdout": "/path/to/tmp/",
     "~followup_annotations": [
       "@@@STEP_LOG_END@Captured Output@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[build]\\scripts\\slave\\runtest.py",
       "--target",
       "Release_x64",
       "--factory-properties",
       "{\"bisect_config\": {\"bad_revision\": \"300148\", \"bug_id\": \"425582\", \"builder_host\": \"master4.golo.chromium.org\", \"builder_port\": \"8341\", \"command\": \"tools/perf/run_benchmark -v --browser=release page_cycler.intl_ar_fa_he\", \"good_revision\": \"300138\", \"gs_bucket\": \"chrome-perf\", \"max_time_minutes\": \"5\", \"metric\": \"warm_times/page_load_time\", \"repeat_count\": \"2\", \"test_type\": \"perf\", \"truncate_percent\": \"25\"}, \"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"build_data_dir\": \"[ROOT]\\\\build_data_dir\", \"buildername\": \"win64_nv_tester\", \"buildnumber\": 571, \"job_name\": \"f7a7b4135624439cbd27fdd5133d74ec\", \"mastername\": \"tryserver.chromium.perf\", \"parent_build_archive_url\": \"gs://test-domain/test-archive.zip\", \"parent_buildername\": \"Win x64 Builder\", \"parent_got_revision\": \"1111111\", \"recipe\": \"chromium\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}",
       "--build-properties",
       "{\"bisect_config\": {\"bad_revision\": \"300148\", \"bug_id\": \"425582\", \"builder_host\": \"master4.golo.chromium.org\", \"builder_port\": \"8341\", \"command\": \"tools/perf/run_benchmark -v --browser=release page_cycler.intl_ar_fa_he\", \"good_revision\": \"300138\", \"gs_bucket\": \"chrome-perf\", \"max_time_minutes\": \"5\", \"metric\": \"warm_times/page_load_time\", \"repeat_count\": \"2\", \"test_type\": \"perf\", \"truncate_percent\": \"25\"}, \"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"build_data_dir\": \"[ROOT]\\\\build_data_dir\", \"buildername\": \"win64_nv_tester\", \"buildnumber\": 571, \"job_name\": \"f7a7b4135624439cbd27fdd5133d74ec\", \"mastername\": \"tryserver.chromium.perf\", \"parent_build_archive_url\": \"gs://test-domain/test-archive.zip\", \"parent_buildername\": \"Win x64 Builder\", \"parent_got_revision\": \"1111111\", \"recipe\": \"chromium\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}",
       "--step-name=Performance Test 2 of 2",
       "--builder-name=win64_nv_tester",
       "--slave-name=TestSlavename",
       "--build-number=571",
-      "tools/perf/run_benchmark.exe",
+      "--run-python-script",
+      "tools/perf/run_benchmark",
       "-v",
       "--browser=release",
       "page_cycler.intl_ar_fa_he"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "Performance Test 2 of 2",
     "stderr": "/path/to/tmp/",
     "stdout": "/path/to/tmp/",
     "~followup_annotations": [
       "@@@STEP_LOG_END@Captured Output@@@"
@@ skipping 38 matching lines @@
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "process_dumps"
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]