[Telemetry] Move TestStreamOutput to unittest_util.

tools/telemetry/telemetry/unittest_util/stream.py

Index: tools/telemetry/telemetry/unittest_util/stream.py
diff --git a/tools/telemetry/telemetry/unittest_util/stream.py b/tools/telemetry/telemetry/unittest_util/stream.py
new file mode 100644
index 0000000000000000000000000000000000000000..4d97ab4cbe291b4cd69ebe85cf48c54973027592
--- /dev/null
+++ b/tools/telemetry/telemetry/unittest_util/stream.py
@@ -0,0 +1,18 @@
+# Copyright 2015 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 TestOutputStream(object):
+  def __init__(self):
+    self._output_data = []
+
+  @property
+  def output_data(self):
+    return ''.join(self._output_data)
+
+  def write(self, data):
+    self._output_data.append(data)
+
+  def flush(self):
+    pass