Change-Id: I9f5b9e59e8cdadf65e80077fe2d3a9822b4592fe
Support diffing deleted revisions, user-supplied text, and additional properties about the diffed revisions such as the user and edit summary. Bug: T20189 Bug: T30047 Bug: T164529 Change-Id: I5565d717d9c2fd19da7cae02890a15e244cc238b