[telemetry] Add TraceResult as return value from tracing, and placeholder trace_event_importer.

tools/telemetry/telemetry/trace_result.py

Index: tools/telemetry/telemetry/trace_result.py
diff --git a/tools/telemetry/telemetry/trace_result.py b/tools/telemetry/telemetry/trace_result.py
new file mode 100644
index 0000000000000000000000000000000000000000..e2d851c84d4740b9306722124868894807427cbb
--- /dev/null
+++ b/tools/telemetry/telemetry/trace_result.py
@@ -0,0 +1,16 @@
+# Copyright (c) 2012 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 TraceResult(object):
+  def __init__(self, impl):
+    self._impl = impl
+
+  def Serialize(self, f):
+    """Serializes the trace result to a file-like object"""
+    return self._impl.Serialize(f)
+
+  def AsTimelineModel(self):
+    """Parses the trace result into a timeline model for in-memory
+    manipulation."""
+    return self._impl.AsTimelineModel()