combine base_unittest.py modules from gm and tools

gm/rebaseline_server/imagediffdb_test.py

Index: gm/rebaseline_server/imagediffdb_test.py
diff --git a/gm/rebaseline_server/imagediffdb_test.py b/gm/rebaseline_server/imagediffdb_test.py
index 4fc8c66f2ba534fc7e50bdf2dc716fbaf5a2e2a5..4cb40e2b051e570c5a3c69589236854f80a10097 100755
--- a/gm/rebaseline_server/imagediffdb_test.py
+++ b/gm/rebaseline_server/imagediffdb_test.py
@@ -26,11 +26,11 @@ IMG_URL_BASE = ('http://chromium-skia-gm.commondatastorage.googleapis.com/gm/'
 class ImageDiffDbTest(unittest.TestCase):
 
   def setUp(self):
-    self._temp_dir = tempfile.mkdtemp()
+    self.temp_dir = tempfile.mkdtemp()
     self.maxDiff = None
 
   def tearDown(self):
-    shutil.rmtree(self._temp_dir)
+    shutil.rmtree(self.temp_dir)
 
   def shortDescription(self):
     """Tell unittest framework to not print docstrings for test cases."""
@@ -76,7 +76,7 @@ class ImageDiffDbTest(unittest.TestCase):
     ]
 
     # Add all image pairs to the database
-    db = imagediffdb.ImageDiffDB(self._temp_dir)
+    db = imagediffdb.ImageDiffDB(self.temp_dir)
     for selftest in selftests:
       retval = db.add_image_pair(
           expected_image_locator=selftest[0], expected_image_url=selftest[1],