Added function to get native path case on Windows and OSX.

tools/isolate/isolate.py

 #!/usr/bin/env python
 # Copyright (c) 2012 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.
 
 """Does one of the following depending on the --mode argument:
   check     Verifies all the inputs exist, touches the file specified with
             --result and exits.
   hashtable Puts a manifest file and hard links each of the inputs into the
             output directory.
@@ skipping 373 matching lines @@
 
   It constructs the equivalent of dictfiles. It is hardcoded to base the
   checkout at src/.
   """
   logging.info(
       'Running %s, cwd=%s' % (
           data['command'], os.path.join(indir, data['relative_cwd'])))
   product_dir = None
   if data['resultdir'] and indir:
     # Defaults to none if both are the same directory.
-    product_dir = os.path.relpath(data['resultdir'], indir) or None
+    try:
+      product_dir = os.path.relpath(data['resultdir'], indir) or None
+    except ValueError:
+      # This happens on Windows if data['resultdir'] is one drive, let's say
+      # 'C:\' and indir on another one like 'D:\'.
+      product_dir = None
   if not data['command']:
     print 'No command to run'
     return 1
   return trace_inputs.trace_inputs(
       data['resultfile'],
       data['command'],
       indir,
       data['relative_cwd'],
       product_dir,
       False)
@@ skipping 27 matching lines @@
     variable = os.path.abspath(variable)
     # All variables are relative to the input file.
     variables[i] = os.path.relpath(variable, isolate_dir)
 
   command, infiles, read_only = load_isolate(
       open(input_file, 'r').read(), variables, error)
 
   # The trick used to determine the root directory is to look at "how far" back
   # up it is looking up.
   # TODO(maruel): Stop the msbuild generator from generating a mix of / and \\.
-  root_dir = isolate_dir.replace(os.path.sep, '/')
+  isolate_dir_replaced = isolate_dir.replace(os.path.sep, '/')
+  root_dir = isolate_dir_replaced
+  logging.debug('root_dir before searching: %s' % root_dir)
   for i in infiles:
     i = i.replace(os.path.sep, '/')
     x = isolate_dir.replace(os.path.sep, '/')
     while i.startswith('../'):
       i = i[3:]
       assert not i.startswith('/')
       x = posixpath.dirname(x)
     if root_dir.startswith(x):
       root_dir = x
   root_dir = root_dir.replace('/', os.path.sep)
+  logging.debug('root_dir after searching: %s' % root_dir)
+
   # The relative directory is automatically determined by the relative path
   # between root_dir and the directory containing the .isolate file.
-  relative_dir = os.path.relpath(isolate_dir, root_dir)
+  relative_dir = os.path.relpath(isolate_dir, root_dir).replace(
+      os.path.sep, '/')
   logging.debug('relative_dir: %s' % relative_dir)
 
   logging.debug(
       'variables: %s' % ', '.join(
         '%s=%s' % (k, v) for k, v in variables.iteritems()))
 
   data = load_results(resultfile)
 
   command, infiles, read_only = load_isolate(
       open(input_file, 'r').read(), variables, error)
@@ skipping 79 matching lines @@
         data)
   except run_test_from_archive.MappingError, e:
     print >> sys.stderr, str(e)
     return 1
   save_results(options.result, data)
   return resultcode
 
 
 if __name__ == '__main__':
   sys.exit(main())