MPEG4Source: fix fragmented read.

Test: passed CTS test DecoderTest#testDecodeFragmented
Bug: 64314728
Bug: 36571704
Change-Id: I71ad6aaae473b03483f8405899d3178148597bba
(cherry picked from commit ba9af7792dfed6e9b1b216aab91a97e713eec891)
(cherry picked from commit 6b401a337674f2f22b7589534700a33187899869)
1 file changed