Add FileDataSink.
ResponseCacheMiddleware: Expose entry metadata and body indices.

Change-Id: I083312e12d85b573d770699c978c2f61a6ef32ae
AsyncHttpRequest: do not set host when there is none.

Change-Id: I20c72374f7aad7d10871cab0e82cbee5972fc2c9
DiskLruCache: Add a way to commit ignoring whether the file was written.
This is kinda hacky. But Streams suck, and I needed a way to do this.

Change-Id: If3f1e9f27a4f1b6d1e1f01342999426542316ba8