DO NOT MERGE: MPEG4Extractor: ensure returned status is checked.

Also fix handling of zero atom size in MPEG4Source::parseChunk.
IDataSource: ensure readAt returns correct status.
Test: manually test with mediaplayer.
Bug: 34718515
Change-Id: I1219ec579aa0876dc1230e36af46b158b84c6d77

(cherry picked from commit ff1fb4d5cdd3b2b28c69edd8cd3021e335ca381a)
(cherry picked from commit 0addb449566857af3f62499fe7056dfba3400a2e)

Change-Id: I1967eb4f8c81101075dcccb7432dcc74d54d75f6
2 files changed