FileInfo: Include size delta

Reviewers are interested in the size of a change that was done to a
file. This is why for non-binary files the number of inserted/deleted
lines is shown. For binary files there is no indication of how big the
change was. With this change we compute for the file size delta in
bytes and return it in the FileInfo. The client can use this
information to show the file size increase/decrease in the file list
(not done in this change).

Please note that a field was added to PatchListEntry and hence the
diff cache must be flushed once.

Change-Id: I0252387099c724251b71480c36b52b7f8d46e713
Signed-off-by: Edwin Kempin <ekempin@google.com>

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/common/FileInfo.java

@@ -20,4 +20,5 @@ public class FileInfo {
   public String oldPath;
   public Integer linesInserted;
   public Integer linesDeleted;
+  public long sizeDelta;
 }