Http cache: Make sure that we handle byte range requests that

end up skipping the cache.

BUG=26175
TEST=unittests


Review URL: http://codereview.chromium.org/348053

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@30877 0039d316-1c4b-4281-b951-d872f2087c98