add unittest for render_pictures binary

tools/test_rendering.py

 '''
-Compares the rendererings of serialized SkPictures to expected result.
-
 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 result.
+
+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
 import optparse
 import sys
 import shutil
 import tempfile
 
 USAGE_STRING = 'Usage: %s input... expectedDir render_app [reander_app_args]'
 HELP_STRING = '''
@@ skipping 91 matching lines @@
 
     if (diff_dir_option):
         diff_dir = diff_dir_option
     else:
         diff_dir = tempfile.mkdtemp()
     try:    
         RenderSkps(inputs, render_dir, render_app, render_args)
         DiffRenderings(expected_dir, render_dir, diff_dir)
     finally:
         Cleanup(render_dir_option, diff_dir_option, render_dir, diff_dir)