Replace linux-specific code in test scripts.

testing/tools/text_diff.py

+#!/usr/bin/env python
+# Copyright 2015 The PDFium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import difflib
+import sys
+
+def main(argv):
+  if len(argv) != 3:
+     print '%s: invalid arguments' % argv[0]
+     return 2
+  filename1 = argv[1]
+  filename2 = argv[2]
+  try:
+    with open(filename1, "r") as f1:
+      str1 = f1.readlines();
+    with open(filename2, "r") as f2:
+      str2 = f2.readlines();
+    diffs = difflib.unified_diff(
+        str1, str2, fromfile=filename1, tofile=filename2)
+  except Exception as e:
+    print "something went astray: %s" % e
+    return 1
+  status_code = 0
+  for diff in diffs:
+    sys.stdout.write(diff)
+    status_code = 1
+  return status_code
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv))