Introduce TracingController and TracingControllerBackend skeleton

tools/telemetry/telemetry/core/platform/tracing_category_filter.py

Index: tools/telemetry/telemetry/core/platform/tracing_category_filter.py
diff --git a/tools/telemetry/telemetry/core/platform/tracing_category_filter.py b/tools/telemetry/telemetry/core/platform/tracing_category_filter.py
new file mode 100644
index 0000000000000000000000000000000000000000..da83643aab52cba1dbcc55f83a0509719fbfa3ec
--- /dev/null
+++ b/tools/telemetry/telemetry/core/platform/tracing_category_filter.py
@@ -0,0 +1,75 @@
+# 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.
+
+class TracingCategoryFilter(object):
+  """A set of included and excluded categories that should be traced.
+
+  The TraceCategoryFilter allows fine tuning of what data is traced. Basic
+  choice of which tracers to use is done by TracingOptions.
+  """
+  def __init__(self, filter_string=None):
+    self._included_categories = []
+    self._excluded_categories = []
+    self._disabled_by_default_categories = []
+    self._delays = []
+
+    if filter_string == None:
+      return
+
+    for category in filter_string.split(','):
+      if category == '':
+        continue
+
+      if category.startswith('DELAY('):
+        self._delays.append(category)
+        continue
+
+      if category[0] == '-':
+        self._excluded_categories.append(category[1:])
+        continue
+
+      if category.startswith('disabled-by-default-'):
+        self._disabled_by_default_categories.append(category)
+        continue
+
+      self.included_categories.append(category)
+
+  @property
+  def included_categories(self):
+    return self._included_categories
+
+  @property
+  def excluded_categories(self):
+    return self._excluded_categories
+
+  @property
+  def disabled_by_default_categories(self):
+    return self._disabled_by_default_categories
+
+  @property
+  def delays(self):
+    return self._delays
+
+  @property
+  def filter_string(self):
+    # Note: This outputs fields in an order that intentionally matches
+    # trace_event_impl's CategoryFilter string order.
+    categories = []
+    categories += self._included_categories
+    categories += self._disabled_by_default_categories
+    categories += ['-%s' % x for x in self._excluded_categories]
+    categories += self._delays
+    return ','.join(categories)
+
+  def AddIncludedCategory(self, category_glob):
+    """Explicitly enables anything matching category_glob."""
+    assert not category_glob.startswith('disabled-by-default-')
+    if category_glob not in self._included_categories:
+      self._included_categories.append(category_glob)
+
+  def AddExcludedCategory(self, category_glob):
+    """Explicitly disables anything matching category_glob."""
+    assert not category_glob.startswith('disabled-by-default-')
+    if category_glob not in self._excluded_categories:
+      self._excluded_categories.append(category_glob)