add unittest for render_pictures binary

tools/test_pictures.py

Index: tools/test_pictures.py
diff --git a/tools/test_pictures.py b/tools/test_pictures.py
index b2397c4ddafca7bbe44732639ea5653e68d9fad2..7ccb3b87315d7d34fa71a657373cc7972270a730 100644
--- a/tools/test_pictures.py
+++ b/tools/test_pictures.py
@@ -1,13 +1,15 @@
 '''
-Compares the rendererings of serialized SkPictures to expected images.
-
-Launch with --help to see more information.
-
-
 Copyright 2012 Google Inc.
 
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
+
+Compares the rendererings of serialized SkPictures to expected images.
+
+Launch with --help to see more information.
+
+TODO(epoger): Combine with overlapping tools/tests/render_pictures_test.py .
+See https://code.google.com/p/skia/issues/detail?id=1943#c2
 '''
 # common Python modules
 import os