Force all OSes to use '/' as the separator

Replace os.sep to '/' in histogram_paths.py to make sure that any
OS should output the same histogram index file.

Bug: 1126500
Change-Id: I5362321237723abda63cc8b2b3d30d0327a9b8a4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2402761
Auto-Submit: Weilun Shi <sweilun@chromium.org>
Commit-Queue: Jesse Doherty <jwd@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#806335}

tools/metrics/histograms/histogram_paths.py

@@ -2,7 +2,6 @@
 # Copyright 2020 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.
-
 """Paths to description XML files in this directory."""
 
 import os
@@ -20,8 +19,8 @@ def _FindHistogramsXmlFiles():
       if (filename == 'histograms.xml'
           or filename == 'histogram_suffixes_list.xml'):
         # Compute the relative path of the histograms xml file.
-        file_path = os.path.relpath(
-          os.path.join(dirName, filename), PATH_TO_HISTOGRAMS_XML_DIR)
+        file_path = os.path.relpath(os.path.join(dirName, filename),
+                                    PATH_TO_HISTOGRAMS_XML_DIR)
         file_list.append(
             os.path.join('tools/metrics/histograms/histograms_xml', file_path))
   return sorted(file_list)
@@ -69,7 +68,9 @@ HISTOGRAMS_INDEX = path_util.GetInputFile(
 
 def main():
   with open(HISTOGRAMS_INDEX, 'w+') as f:
-    f.write("\n".join(HISTOGRAMS_XMLS_RELATIVE))
+    # Force all OSes to use '/' as the separator.
+    f.write("\n".join(
+        [path.replace(os.sep, '/') for path in HISTOGRAMS_XMLS_RELATIVE]))
 
 
 if __name__ == '__main__':