Convert Windows to POSIX path when calling scm.GIT.CaptureStatus().

Fixes problem in this thread:

http://groups.google.com/a/chromium.org/group/chromium-dev/browse_thread/thread/6098b2d0136e650e#

This was broken by http://crrev.com/102930, when I made GIT's GenerateDiff() use scm.GIT.CaptureStatus() instead of scm.GIT.GetDifferentFiles().

(Thanks Scott Graham for figuring out the problem!)

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/8083003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@103302 0039d316-1c4b-4281-b951-d872f2087c98

trychange.py

@@ -283,7 +283,8 @@ class GIT(SCM):
     logging.info("GIT(%s)" % self.checkout_root)
 
   def CaptureStatus(self):
-    return scm.GIT.CaptureStatus(self.checkout_root, self.diff_against)
+    return scm.GIT.CaptureStatus(self.checkout_root.replace(os.sep, '/'),
+                                 self.diff_against)
 
   def GenerateDiff(self):
     return scm.GIT.GenerateDiff(self.checkout_root, files=self.files,