rebaseline_server: write JSON files using Unix line endings, even on Windows

gm/gm_json.py

 #!/usr/bin/env python
 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Schema of the JSON summary file written out by the GM tool.
 
 This must be kept in sync with the kJsonKey_ constants in gm_expectations.cpp !
 """
 
 __author__ = 'Elliot Poger'
 
 
 # system-level imports
+import io
 import json
 import os
 
 
 # Key strings used in GM results JSON files (both expected-results.json and
 # actual-results.json).
 #
 # These constants must be kept in sync with the kJsonKey_ constants in
 # gm_expectations.cpp !
 
@@ skipping 92 matching lines @@
   return json_dict
 
 def LoadFromFile(file_path):
   """Loads the JSON summary written out by the GM tool.
      Returns a dictionary keyed by the values listed as JSONKEY_ constants
      above."""
   file_contents = open(file_path, 'r').read()
   return LoadFromString(file_contents)
 
 def WriteToFile(json_dict, file_path):
-  """Writes the JSON summary in json_dict out to file_path."""
-  with open(file_path, 'w') as outfile:
-    json.dump(json_dict, outfile, sort_keys=True, indent=2)
+  """Writes the JSON summary in json_dict out to file_path.
+
+  The file is written Unix-style (each line ends with just LF, not CRLF);
+  see https://code.google.com/p/skia/issues/detail?id=1815 for reasons."""
+  with io.open(file_path, mode='w', newline='', encoding='utf-8') as outfile:
+    outfile.write(unicode(json.dumps(json_dict, outfile, sort_keys=True,
+                                     indent=2)))