Add a pattern to the anonymizer tool to catch and anonymize Universal
Unique Identidiers (UUIDs).

BUG=721115
TEST=components_unittests --gtest_filter=AnonymizerToolTest.AnonymizeCustomPatterns

Review-Url: https://codereview.chromium.org/2905723002
Cr-Commit-Position: refs/heads/master@{#474420}