Pass chartjson_result_file to gtest_parallel tests.

Translate --isolate-script-test-perf-output to --chartjson_result_file
and pass it to the test.
That way we can use Chromium's recipe code to report results to the
Perf dashboard.

TBR=phoglund@webrtc.org

Bug: chromium:807737
Change-Id: I2d3479fe29431cc1a8faf9a73b054a5f4ec610a4
Reviewed-on: https://webrtc-review.googlesource.com/47121
Commit-Queue: Edward Lemur <ehmaldonado@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21894}

tools_webrtc/gtest-parallel-wrapper.py

@@ -107,8 +107,7 @@ def _ParseArgs():
   parser.add_argument('--store-test-artifacts', action='store_true',
                       default=False)
 
-  # We don't need to implement this flag, and possibly can't, since it's
-  # intended for results of Telemetry tests. See
+  # Used to store results of perf tests. See
   # https://chromium.googlesource.com/external/github.com/catapult-project/catapult/+/HEAD/dashboard/docs/data-format.md
   parser.add_argument('--isolated-script-test-perf-output', type=str,
                       default=None)
@@ -146,6 +145,13 @@ def _ParseArgs():
         test_artifacts_dir,
     ]
 
+  # The corresponding flag in WebRTC is called 'chartjson_result_file'.
+  if options.isolated_script_test_perf_output:
+    executable_args += [
+        '--chartjson_result_file',
+        options.isolated_script_test_perf_output,
+    ]
+
   # GTEST_SHARD_INDEX and GTEST_TOTAL_SHARDS must be removed from the
   # environment. Otherwise it will be picked up by the binary, causing a bug
   # where only tests in the first shard are executed.