[tools/perf] Fix links to local traces in traceUrls diagnostic

Bug: 1027074
Change-Id: I077c164aaa59ee6644f9f05ee61a26944d6a23c6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1928701
Commit-Queue: Mikhail Khokhlov <khokhlov@google.com>
Reviewed-by: Juan Antonio Navarro Pérez <perezju@chromium.org>
Cr-Commit-Position: refs/heads/master@{#717639}

tools/perf/core/results_processor/processor.py

@@ -259,11 +259,15 @@ def UploadArtifacts(test_result, upload_bucket, run_identifier):
                  artifact['remoteUrl'])
 
 
-def _GetTraceUrl(test_result):
+def GetTraceUrl(test_result):
   artifacts = test_result.get('outputArtifacts', {})
   trace_artifact = artifacts.get(compute_metrics.HTML_TRACE_NAME, {})
-  return (trace_artifact['remoteUrl'] if 'remoteUrl' in trace_artifact
-               else trace_artifact.get('filePath'))
+  if 'remoteUrl' in trace_artifact:
+    return trace_artifact['remoteUrl']
+  elif 'filePath' in trace_artifact:
+    return 'file://' + trace_artifact['filePath']
+  else:
+    return None
 
 
 def AddDiagnosticsToHistograms(test_result, test_suite_start, results_label,
@@ -295,7 +299,7 @@ def AddDiagnosticsToHistograms(test_result, test_suite_start, results_label,
   story_tags = [tag['value'] for tag in test_result.get('tags', [])
                 if tag['key'] == 'story_tag']
   result_id = int(test_result.get('resultId', 0))
-  trace_url = _GetTraceUrl(test_result)
+  trace_url = GetTraceUrl(test_result)
 
   additional_diagnostics = [
       (reserved_infos.BENCHMARKS, test_suite),

tools/perf/core/results_processor/processor_unittest.py

@@ -148,3 +148,28 @@ class ResultsProcessorUnitTests(unittest.TestCase):
   def testMeasurementToHistogramUnknownUnits(self):
     with self.assertRaises(ValueError):
       processor.MeasurementToHistogram('a', {'unit': 'yards', 'samples': [9]})
+
+  def testGetTraceUrlRemote(self):
+    test_result = testing.TestResult(
+        'benchmark/story',
+        output_artifacts={
+            'trace.html': testing.Artifact('trace.html', 'gs://trace.html')
+        },
+    )
+    url = processor.GetTraceUrl(test_result)
+    self.assertEqual(url, 'gs://trace.html')
+
+  def testGetTraceUrlLocal(self):
+    test_result = testing.TestResult(
+        'benchmark/story',
+        output_artifacts={
+            'trace.html': testing.Artifact('trace.html')
+        },
+    )
+    url = processor.GetTraceUrl(test_result)
+    self.assertEqual(url, 'file://trace.html')
+
+  def testGetTraceUrlEmpty(self):
+    test_result = testing.TestResult('benchmark/story')
+    url = processor.GetTraceUrl(test_result)
+    self.assertIsNone(url)