Mms: Fix failure when sharing image via 3rd apk without file extension

After sharing image via xunleikankan, messaging receives a file uri, but
the image name in uri does not have file extension, it causes messaging
to not be able to get content type and refuse to attach image.

Use decoding image data's content type if get content type with uri failed.

Change-Id: Ie29501869f9b494c1f4838ed66e42eb8981fe2a3
CRs-Fixed: 907468
1 file changed