Don't throw needlessly when returning the CacheResponse.
We were throwing under the premise that we'd always have
response headers before we had a cached body. But when the
user calls connect() we'll have queried the cache but we
won't necessarily have response headers from the server yet.
That's because connect() doesn't require a response to be ready.
Bug: http://b/5920659
Cherry-picked from: I9d69b44b5be3d0e29f14d8b83781f6e65c67582a
Change-Id: Ia403b42ddc9783fd1456164f4b7350da3ce80566
2 files changed
