Add a tool to look for unused suppressions.

tools/valgrind/unused_suppressions.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.
+
+import sys
+import urllib2
+
+import suppressions
+
+
+def main():
+  supp = suppressions.GetSuppressions()
+
+  all_supps = []
+  for supps in supp.values():
+    all_supps += [s.description for s in supps]
+  sys.stdout.write(urllib2.urlopen(
+      'http://chromium-build-logs.appspot.com/unused_suppressions',
+      '\n'.join(all_supps)).read())
+  return 0
+
+if __name__ == "__main__":
+  sys.exit(main())