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

scripts/slave/recipes/bisection/desktop_bisect.expected/basic_linux_bisect_tester_recipe.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]/resources/bot_update.py",
       "--master",
       "tryserver.chromium.perf",
       "--builder",
       "linux_perf_bisect",
@@ skipping 257 matching lines @@
       "Release",
       "--xvfb",
       "--factory-properties",
       "{\"bisect_config\": {\"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\", \"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\"], \"branch\": \"\", \"buildername\": \"linux_perf_bisect\", \"buildnumber\": 571, \"issue\": 12853011, \"job_name\": \"f7a7b4135624439cbd27fdd5133d74ec\", \"mastername\": \"tryserver.chromium.perf\", \"parent_build_archive_url\": \"gs://test-domain/test-archive.zip\", \"parent_got_revision\": \"1111111\", \"patch_project\": \"chromium\", \"patchset\": 1, \"project\": \"chrome\", \"recipe\": \"bisection/desktop_bisect\", \"repository\": \"\", \"requester\": \"commit-bot@chromium.org\", \"revision\": \"HEAD\", \"rietveld\": \"https://codereview.chromium.org\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}",
       "--build-properties",
       "{\"bisect_config\": {\"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\", \"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\"], \"branch\": \"\", \"buildername\": \"linux_perf_bisect\", \"buildnumber\": 571, \"issue\": 12853011, \"job_name\": \"f7a7b4135624439cbd27fdd5133d74ec\", \"mastername\": \"tryserver.chromium.perf\", \"parent_build_archive_url\": \"gs://test-domain/test-archive.zip\", \"parent_got_revision\": \"1111111\", \"patch_project\": \"chromium\", \"patchset\": 1, \"project\": \"chrome\", \"recipe\": \"bisection/desktop_bisect\", \"repository\": \"\", \"requester\": \"commit-bot@chromium.org\", \"revision\": \"HEAD\", \"rietveld\": \"https://codereview.chromium.org\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}",
       "--step-name=Performance Test 1 of 2",
       "--builder-name=linux_perf_bisect",
       "--slave-name=TestSlavename",
       "--build-number=571",
+      "--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",
       "--xvfb",
       "--factory-properties",
       "{\"bisect_config\": {\"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\", \"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\"], \"branch\": \"\", \"buildername\": \"linux_perf_bisect\", \"buildnumber\": 571, \"issue\": 12853011, \"job_name\": \"f7a7b4135624439cbd27fdd5133d74ec\", \"mastername\": \"tryserver.chromium.perf\", \"parent_build_archive_url\": \"gs://test-domain/test-archive.zip\", \"parent_got_revision\": \"1111111\", \"patch_project\": \"chromium\", \"patchset\": 1, \"project\": \"chrome\", \"recipe\": \"bisection/desktop_bisect\", \"repository\": \"\", \"requester\": \"commit-bot@chromium.org\", \"revision\": \"HEAD\", \"rietveld\": \"https://codereview.chromium.org\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}",
       "--build-properties",
       "{\"bisect_config\": {\"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\", \"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\"], \"branch\": \"\", \"buildername\": \"linux_perf_bisect\", \"buildnumber\": 571, \"issue\": 12853011, \"job_name\": \"f7a7b4135624439cbd27fdd5133d74ec\", \"mastername\": \"tryserver.chromium.perf\", \"parent_build_archive_url\": \"gs://test-domain/test-archive.zip\", \"parent_got_revision\": \"1111111\", \"patch_project\": \"chromium\", \"patchset\": 1, \"project\": \"chrome\", \"recipe\": \"bisection/desktop_bisect\", \"repository\": \"\", \"requester\": \"commit-bot@chromium.org\", \"revision\": \"HEAD\", \"rietveld\": \"https://codereview.chromium.org\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}",
       "--step-name=Performance Test 2 of 2",
       "--builder-name=linux_perf_bisect",
       "--slave-name=TestSlavename",
       "--build-number=571",
+      "--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": [
@@ skipping 28 matching lines @@
     "~followup_annotations": [
       "@@@STEP_LINK@gsutil.upload@https://storage.cloud.google.com/chrome-perf/bisect-results/f7a7b4135624439cbd27fdd5133d74ec.results@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]