download_baselines.py : only set svn properties of files whose content has changed

and while I was at it, sort the filenames before acting on them, to make the output easier to read

BUG=http://code.google.com/p/skia/issues/detail?id=618
Review URL: https://codereview.appspot.com/6223061

git-svn-id: http://skia.googlecode.com/svn/trunk@4031 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tools/svn.py b/tools/svn.py
index b2f010c..1fd1120 100644
--- a/tools/svn.py
+++ b/tools/svn.py
@@ -92,5 +92,5 @@
         @param property_value what to set the property_name to
         """
         all_files = os.listdir(self._directory)
-        matching_files = fnmatch.filter(all_files, filename_pattern)
+        matching_files = sorted(fnmatch.filter(all_files, filename_pattern))
         self.SetProperty(matching_files, property_name, property_value)