Consider pass an expected result if a test is NeedsRebaseline/NeedsManualRebaseline.

It's common practice to rebaseline the port you are working on and
add a generid NeedsRebaseline line. I think that's fine and we should
not treat that case as an unexpected pass.

Unexpected pass is only useful insofar as it implies that someone
should be removing a TestExpectations line, which doesn't apply
if the test needs rebaselineing (i.e. it's already someone's
responsibility to remove that line).

Review URL: https://chromiumcodereview.appspot.com/20124005

git-svn-id: svn://svn.chromium.org/blink/trunk@154946 bbb929c8-8fbe-4397-9dbb-9b2b20218538