Fix various errors in FileURLConnectionTest.

- First, the test was broken pretty badly. It would pass a
  Jar style URL to a FileURLConnection and expect it to
  work, this is out of spec and seems wrong in general
  (file:///foo.apk!resources/foo.txt).

- The RI supports various "headers" on file URL connections
  (sigh). As if the getHeaderField(int) and getHeaderFieldKey(int)
  APIs weren't bad enough. This has now been implemented with
  a naive implementation.

- Fixes FileURLConnection to populate a header map for
  information it provides (content length, content type
  etc.)

bug: 11664881

Change-Id: I7a3e9aaa79bf125abbcfe8367574115ce54718e3
3 files changed