DefaultFileNameMap: Support extensions that contain '.'.

Android 10 added many new MIME mappings, with one extension (pcf.Z)
containing a '.'. URLConnection.getFileNameMap() treated the part
of the filename after the last '.' as the extension, so it only
checked 'Z' and didn't recognize 'pcf.Z'.

This CL fixes this by letting DefaultFileNameMap pick the longest
filename suffix that follows a '.' and is a known extension. This
means that after this CL,
  URLConnection.getFileNameMap().getContentTypeFor("fileName.pcf.Z")
will now return "application/x-font-pcf" because it looks up "pcf.Z"
before attempting "Z". Previously, it would have returned null because
the logic would only have considered "Z", which is not a known
extension.

For backwards compatibility with historic versions of Android, if
filename contains no '.' then the whole filename is also considered
as an extension, but only if the filename didn't contain a path
component ('/'). The details of this historic behavior seem somewhat
accidental and may be changed in a future CL, but that is orthogonal
to this change.

Bug: 141880067
Test: atest CtsLibcoreTestCases:libcore.java.net.URLConnectionTest

Change-Id: I3da4ec4491a8eef74e8874d1a5c43fcfa523c3f8

0 files changed, 0 insertions, 0 deletions