[Telemetry] Make --chartjson output chart.json instead of to stdout.

tools/telemetry/telemetry/results/chart_json.py

-# Copyright 2014 The Chromium Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-import collections
-import itertools
-
-from telemetry.value import summary as summary_module
-
-def ResultsAsChartDict(benchmark_metadata, page_specific_values,
-                       summary_values):
-  """Produces a dict for serialization to Chart JSON format from raw values.
-
-  Chart JSON is a transformation of the basic Telemetry JSON format that
-  removes the page map, summarizes the raw values, and organizes the results
-  by chart and trace name. This function takes the key pieces of data needed to
-  perform this transformation (namely, lists of values and a benchmark metadata
-  object) and processes them into a dict which can be serialized using the json
-  module.
-
-  Design doc for schema: http://goo.gl/kOtf1Y
-
-  Args:
-    page_specific_values: list of page-specific values
-    summary_values: list of summary values
-    benchmark_metadata: a benchmark.BenchmarkMetadata object
-
-  Returns:
-    A Chart JSON dict corresponding to the given data.
-  """
-  summary = summary_module.Summary(page_specific_values)
-  values = itertools.chain(
-      summary.interleaved_computed_per_page_values_and_summaries,
-      summary_values)
-  charts = collections.defaultdict(dict)
-
-  for value in values:
-    if value.page:
-      chart_name, trace_name = (
-          value.GetChartAndTraceNameForPerPageResult())
-    else:
-      chart_name, trace_name = (
-          value.GetChartAndTraceNameForComputedSummaryResult(None))
-      if chart_name == trace_name:
-        trace_name = 'summary'
-
-    assert trace_name not in charts[chart_name]
-
-    charts[chart_name][trace_name] = value.AsDict()
-
-  result_dict = {
-    'format_version': '0.1',
-    'benchmark_name': benchmark_metadata.name,
-    'charts': charts
-  }
-
-  return result_dict