Fix histogram printing for Telemetry tests.

build/android/pylib/perf_tests_helper.py

Index: build/android/pylib/perf_tests_helper.py
diff --git a/build/android/pylib/perf_tests_helper.py b/build/android/pylib/perf_tests_helper.py
index e09221bbf930941fbf1d1a0c09ed6dad073f1587..d227d4153ffe45425f0341d904ec1ea37919f1ad 100644
--- a/build/android/pylib/perf_tests_helper.py
+++ b/build/android/pylib/perf_tests_helper.py
@@ -76,9 +76,7 @@ def PrintPerfResult(measurement, trace, values, units, result_type='default',
     trace: A description of the particular data point, e.g. "reference".
     values: A list of numeric measured values.
     units: A description of the units of measure, e.g. "bytes".
-    result_type: A  tri-state that accepts values of ['unimportant', 'default',
-        'informational']. 'unimportant' prints RESULT, 'default' prints *RESULT
-        and 'informational' prints nothing.
+    result_type: Accepts values of RESULT_TYPES.
     print_to_stdout: If True, prints the output in stdout instead of returning
         the output to caller.
 
@@ -87,28 +85,43 @@ def PrintPerfResult(measurement, trace, values, units, result_type='default',
   """
   assert result_type in RESULT_TYPES, 'result type: %s is invalid' % result_type
 
+  trace_name = _EscapePerfResult(trace)
+
   if result_type in ['unimportant', 'default', 'informational']:
     assert isinstance(values, list)
     assert len(values)
     assert '/' not in measurement
     value, avg, sd = _MeanAndStdDevFromList(values)
+    output = '%s%s: %s%s%s %s' % (
+        RESULT_TYPES[result_type],
+        _EscapePerfResult(measurement),
+        trace_name,
+        # Do not show equal sign if the trace is empty. Usually it happens when
+        # measurement is enough clear to describe the result.
+        '= ' if trace_name else '',
+        value,
+        units)
   else:
-    value = values[0]
-    # We can't print the units, otherwise parsing the histogram json output
-    # can't be parsed easily.
-    units = ''
-    avg, sd = GeomMeanAndStdDevFromHistogram(value)
+    assert(result_type in ['histogram', 'unimportant-histogram'])
+    assert isinstance(values, list)
+    assert len(values)
+    # Print out each histogram separately. We can't print the units, otherwise
+    # the histogram json output can't be parsed easily.
+    output = ''
+    ix = 1
+    for value in values:
+      name = '%s.%s_%d' % (_EscapePerfResult(measurement), trace_name, ix)
+      output += '%s%s%s : %s = %s' % (
+          '\n' if ix > 1 else '',
+          RESULT_TYPES[result_type],
+          name,
+          name,
+          value)
+      ix += 1
+    measurement = '%s.%s' % (measurement, trace_name)
+    means_and_sds = [GeomMeanAndStdDevFromHistogram(value) for value in values]
+    _, avg, sd = _MeanAndStdDevFromList([mean for (mean, _) in means_and_sds ])
 
-  trace_name = _EscapePerfResult(trace)
-  output = '%s%s: %s%s%s %s' % (
-    RESULT_TYPES[result_type],
-    _EscapePerfResult(measurement),
-    trace_name,
-    # Do not show equal sign if the trace is empty. Usually it happens when
-    # measurement is enough clear to describe the result.
-    '= ' if trace_name else '',
-    value,
-    units)
   if avg:
     output += '\nAvg %s: %f%s' % (measurement, avg, units)
   if sd: