[Telemetry] Move TestStreamOutput to unittest_util.

tools/telemetry/telemetry/unittest_util/gtest_progress_reporter_unittest.py

Index: tools/telemetry/telemetry/unittest_util/gtest_progress_reporter_unittest.py
diff --git a/tools/telemetry/telemetry/unittest_util/gtest_progress_reporter_unittest.py b/tools/telemetry/telemetry/unittest_util/gtest_progress_reporter_unittest.py
index 6345a4a357269a9f7caf9290950387dc38c0e3c0..bab63f6b1c815d4cd7941e23bd074007a2aaea59 100644
--- a/tools/telemetry/telemetry/unittest_util/gtest_progress_reporter_unittest.py
+++ b/tools/telemetry/telemetry/unittest_util/gtest_progress_reporter_unittest.py
@@ -8,6 +8,7 @@ import unittest
 from telemetry.core import exceptions
 from telemetry.unittest_util import gtest_progress_reporter
 from telemetry.unittest_util import simple_mock
+from telemetry.unittest_util import stream
 
 
 try:
@@ -23,21 +24,6 @@ class TestFoo(unittest.TestCase):
     pass
 
 
-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
-
-
 class TestResultWithSuccesses(unittest.TestResult):
   def __init__(self):
     super(TestResultWithSuccesses, self).__init__()
@@ -51,7 +37,7 @@ class TestResultWithSuccesses(unittest.TestResult):
 class GTestProgressReporterTest(unittest.TestCase):
   def setUp(self):
     super(GTestProgressReporterTest, self).setUp()
-    self._stream = TestOutputStream()
+    self._stream = stream.TestOutputStream()
     self._formatter = gtest_progress_reporter.GTestProgressReporter(
         self._stream)