cros: Run gtest perf test on device

- Add --trace-dir=PATH to chromeos/test_runner.py
  When present, test_runner script passes the switch with
  device local path (e.g. /tmp) to gtest to generate trace
  file on device and collects the trace files back to PATH
  on host afterwards.
- Update run_gtest_benchmark.py to map the trace file path
  in the test result json collected by test_runner script
  so that processor scripts could find and computer metrics
  from the trace file.

Example usage:

For developers:
  tools/perf/run_gtest_benchmark.py
    out_${SDK_BOARD}/Release/bin/run_interactive_ui_tests
    --device=$DUT
    --gtest_filter=All/OverviewAnimationsTest.EnterExit/7
    --output-dir=/tmp/perf_output
    --output-format=histograms
    --dbus-stub --stop-ui

For perf bots:
  testing/scripts/run_performance_tests.py
    --isolated-script-test-output=/tmp/perf_output/output.json
    --non-telemetry=true
    --use-gtest-benchmark-script
    --gtest-benchmark-name=interactive_ui_tests
    tools/perf/run_gtest_benchmark.py
      out_${SDK_BOARD}/Release/bin/run_interactive_ui_tests
      --device=$DUT
      --output-format=histograms
      --dbus-stub --stop-ui

Bug: 945711
Change-Id: Ia6911921b8354d7763be96c30a8877c9d598f103
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1974587
Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Ben Pastene <bpastene@chromium.org>
Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#726402}

build/chromeos/test_runner.py

@@ -412,6 +412,7 @@ def __init__(self, args, unknown_args):
 
     self._on_device_script = None
     self._stop_ui = args.stop_ui
+    self._trace_dir = args.trace_dir
 
   @property
   def suite_name(self):
@@ -443,6 +444,22 @@ def build_test_command(self):
           result_dir,
       ]
 
+    if self._trace_dir and self._logs_dir:
+      trace_path = os.path.dirname(self._trace_dir) or '.'
+      if os.path.abspath(trace_path) != os.path.abspath(self._logs_dir):
+        raise TestFormatError(
+            '--trace-dir and --logs-dir must point to the same directory.')
+
+    if self._trace_dir:
+      trace_path, trace_dirname = os.path.split(self._trace_dir)
+      device_trace_dir = '/tmp/%s' % trace_dirname
+      self._test_cmd += [
+          '--results-src',
+          device_trace_dir,
+          '--results-dest-dir',
+          trace_path,
+      ]
+
     # Build the shell script that will be used on the device to invoke the test.
     device_test_script_contents = self.BASIC_SHELL_SCRIPT[:]
     if self._llvm_profile_var:
@@ -468,6 +485,14 @@ def build_test_command(self):
     if self._test_launcher_summary_output:
       test_invocation += ' --test-launcher-summary-output=%s' % (
           device_result_file)
+
+    if self._trace_dir:
+      device_test_script_contents.extend([
+          'rm -rf %s' % device_trace_dir,
+          'su chronos -c -- "mkdir -p %s"' % device_trace_dir,
+      ])
+      test_invocation += ' --trace-dir=%s' % device_trace_dir
+
     if self._additional_args:
       test_invocation += ' %s' % ' '.join(self._additional_args)
 
@@ -805,6 +830,11 @@ def main():
       '--stop-ui',
       action='store_true',
       help='Will stop the UI service in the device before running the test.')
+  gtest_parser.add_argument(
+      '--trace-dir',
+      type=str,
+      help='When set, will pass down to the test to generate the trace and '
+      'retrieve the trace files to the specified location.')
 
   # Tast test args.
   # pylint: disable=line-too-long

tools/perf/run_gtest_benchmark.py

@@ -8,6 +8,7 @@
 """
 
 import argparse
+import json
 import os
 import shutil
 import sys
@@ -49,8 +50,40 @@ def RunGTest(options, gtest_args):
   return return_code
 
 
+def _MapDeviceTracePath(trace_dir, result_json):
+  """Maps trace file paths to |trace_dir|. It is needed when gtest runs
+  on a real device and trace file is the absolute path on the device. If
+  gtest runs on a bot, the returned result should be the same as input.
+
+  Args:
+    result_json: JSON string of a test result.
+
+  Returns the JSON string of a LUCI test result with trace file path mapped.
+  """
+  result = json.loads(result_json)
+  test_result = result.get('testResult', {})
+  artifacts = test_result.get('outputArtifacts', {})
+  trace_names = [name for name in artifacts if name.startswith('trace/')]
+  for name in trace_names:
+    trace_file = artifacts[name]['filePath']
+    trace_file = os.path.join(trace_dir, os.path.basename(trace_file))
+    artifacts[name]['filePath'] = trace_file
+
+  if artifacts:
+    result['testResult']['outputArtifacts'] = artifacts
+
+  return json.dumps(result)
+
+
 def _MergeResultsJson(trace_dir, output_file):
-  """Merge results json files generated in each test case into output_file."""
+  """Merge results json files generated in each test case into output_file.
+
+  Gtest test cases store results in LUCI test results format.
+  See: go/luci-test-results-design
+
+  This function reads the individual LUCI test results JSON files and
+  concatenates them into a jsonl file to feed result processor scripts later on.
+  """
   result_files = [
       os.path.join(trace_dir, trace)
       for trace in os.listdir(trace_dir)
@@ -61,7 +94,7 @@ def _MergeResultsJson(trace_dir, output_file):
       with open(result_file) as f:
         stripped_lines = [line.rstrip() for line in f]
         for line in stripped_lines:
-          output.write('%s\n' % line)
+          output.write('%s\n' % _MapDeviceTracePath(trace_dir, line))
 
 
 def ProcessResults(options):