Add Chart JSON processing to Telemetry.

tools/telemetry/telemetry/results/json_output_formatter.py

Index: tools/telemetry/telemetry/results/json_output_formatter.py
diff --git a/tools/telemetry/telemetry/results/json_output_formatter.py b/tools/telemetry/telemetry/results/json_output_formatter.py
index 4298587a603c416c0f0644c32739f4bf227b1b1d..bf23ede9b8452d039c828b6e99720b65c74370b9 100644
--- a/tools/telemetry/telemetry/results/json_output_formatter.py
+++ b/tools/telemetry/telemetry/results/json_output_formatter.py
@@ -6,16 +6,26 @@ import json
 
 from telemetry.results import output_formatter
 
-
-def ResultsAsDict(page_test_results, metadata):
+def ResultsAsDict(page_test_results, benchmark_metadata):
+  """Takes PageTestResults to a dict serializable to JSON.
+
+  To serialize results as JSON we first convert them to a dict that can be
+  serialized by the json module. It also requires a benchmark_metadat object
+  for metadata to be integrated into the results (currently the benchmark
+  name).
+
+  Args:
+    page_test_results: a PageTestResults object
+    benchmark_metadata: a benchmark.BenchmarkMetadata object
+  """
   result_dict = {
     'format_version': '0.2',
-    'benchmark_name': metadata.name,
+    'benchmark_name': benchmark_metadata.name,
     'summary_values': [v.AsDict() for v in
                        page_test_results.all_summary_values],
     'per_page_values': [v.AsDict() for v in
                         page_test_results.all_page_specific_values],
-    'pages': dict((p.id, p.AsDict()) for p in _GetAllPages(page_test_results))
+    'pages': {p.id: p.AsDict() for p in _GetAllPages(page_test_results)}
   }
 
   return result_dict
@@ -26,15 +36,15 @@ def _GetAllPages(page_test_results):
   return pages
 
 class JsonOutputFormatter(output_formatter.OutputFormatter):
-  def __init__(self, output_stream, metadata):
+  def __init__(self, output_stream, benchmark_metadata):
     super(JsonOutputFormatter, self).__init__(output_stream)
-    self._metadata = metadata
+    self._benchmark_metadata = benchmark_metadata
 
   @property
-  def metadata(self):
-    return self._metadata
+  def benchmark_metadata(self):
+    return self._benchmark_metadata
 
   def Format(self, page_test_results):
-    json.dump(ResultsAsDict(page_test_results, self.metadata),
+    json.dump(ResultsAsDict(page_test_results, self.benchmark_metadata),
         self.output_stream)
     self.output_stream.write('\n')