Add a module for tracking categories that metrics depend on.

tools/perf/benchmarks/metric_dependencies.py

+# Copyright 2017 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.
+
+_PREFIX_FOR_EXCLUDED_CATEGORY = '-'
+_PREFIX_FOR_DISABLED_BY_DEFAULT_CATEGORY = 'disabled-by-default-'
+
+# If you add a new metric, then register its categories in this table
+# and use AugmentOptionsForMetrics in the benchmark configuration.
+# TODO(ulan): Add all existing metics to this table.
+_CATEGORIES_FOR_METRICS = {

[nednguyen, 2017/03/02 13:36:00]

ulan: instead of this, I think we should make a all_metrics.json file in
catapult/tracing/tracing/metrics that list out all the metrics & their dependent
tracing categories. 

The reason for this is it would allow the metric side panel in about://tracing
to also use this dependency map, so we can do things like: not displaying
certain metrics in the panel if the trace does not have the required categories,
show people that they will need to enable which categories to get the metric. 

+  'expectedQueueingTimeMetric': [
+    'blink.console', # For ranges in cache_temperature.MarkTelemetryInternal.
+    'blink.user_timing', # For core navigation events.
+    'loading', # For first-meaningful-paint computation.
+    'navigation', # For core navigation events.
+    'toplevel', # For time-to-interactive computation.
+  ],
+  'loadingMetric': [
+    'blink.console', # For ranges in cache_temperature.MarkTelemetryInternal.
+    'blink.user_timing', # For core navigation events.
+    'loading', # For first-meaningful-paint computation.
+    'navigation', # For core navigation events.
+    'toplevel', # For time-to-interactive computation.
+  ],
+}
+
+def AugmentOptionsForMetrics(tbm_options, metrics):
+  """ For each metric in the given metrics list adds its category dependencies
+  to the tracing config of the given tmb_options.
+  Args:
+      tbm_options: An instance of timeline_based_measurement.Options
+      metrics: A list of timeline based metric names.
+  """
+  category_filter = tbm_options.config.chrome_trace_config.category_filter
+  for metric in metrics:
+    assert metric in _CATEGORIES_FOR_METRICS, 'Unknown metric.'
+    categories = _CATEGORIES_FOR_METRICS[metric]
+    for category in categories:
+      if category.startswith(_PREFIX_FOR_EXCLUDED_CATEGORY):
+        category_filter.AddExcludedCategory(category)
+      elif category.startswith(_PREFIX_FOR_DISABLED_BY_DEFAULT_CATEGORY):
+        category_filter.AddDisabledByDefault(category)
+      else:
+        category_filter.AddIncludedCategory(category)
+
+def SetMetricDependenciesForTesting(categories_for_metrics):
+  global _CATEGORIES_FOR_METRICS
+  _CATEGORIES_FOR_METRICS = categories_for_metrics