DWR

In FileHandler / CachingFileHandler:
 if (givenEtag == null) {
     if (modifiedSince > CONTAINER_START_TIME) {
          log.debug("Sending 304

Which is almost good, ">=" should be used.

but if both headers are present:

 if (ETAG.equals(givenEtag) && modifiedSince < CONTAINER_START_TIME) {
          log.debug("Sending 304

Using "<" here contradicts the behaviour above.

Test log:
Sending content for /engine.js, If-Modified-Since=1206465144000, Container Start=1206465144000, Old ETag="1206465144000", New ETag="1206465144000"

This should have been a sending 304 instead in that case.