Review Board 2.0 introduced support for showing entries in the diff

viewer for newly-added empty files. It did this based on whether a file

was new and whether it has 0 non-equals chunks.
That logic should have been whether it has 0 chunks. That was a simple

template change to fix.
However, it exposed a problem where a valid change could have 0 chunks,

once again triggering this problem. That was a result of checking the

normalized insert/delete counts, rather than the raw insert/delete

counts from the diff. That meant that if a change only had replaces, it

would also appear as empty.
This was particularly problematic in combination with a very old design

flaw, where diffs that were based on a parent diff of a newly added file

inherited the "new" state. If a series of files were introduced on a

branch and then commits later in the branch were put up for review, they

could easily show up as empty. Alternatively, if a file contained only

'replace' changes, and was in the same real or bogus new state, it could

also hit this case.

Unit tests pass.
The following scenarios were checked. Each showed the diff as an empty file

before.

Scenario 1: New files, interdiffs without modifications
Created a new file and uploaded the diff. Then posted another diff of that

file without modifications.
When viewing the interdiff between the two, the diff no longer showed up as

an empty file.
Repeated this with a diff containing a parent diff from a newly-added commit,

which transferred the "new" status (from an old design flaw). This failed

before, but worked after.

Scenario 2: New diffs, interdiffs with replace lines only
Repeated the above scenario, but made changes to a single line between the

revisions, generating "replace" chunks. Before, this caused the diff to appear

as empty. Now, it shows the replaced lines.

Scenario 3: Diff with new parent diff and replace lines only
Created a commit introducing a file. Changed a line in the file and posted it.

Turned off showing extra whitespace and viewed it. Saw the empty file.