Transcoder: Added MediaTranscoder and unit test.

MediaTranscoder is the API for the native transcoding library.

Test: Unit tests.
Bug: 156003955, 152091443, 155918341
Change-Id: I24b52d174db0faecea8f331ef6d8a3dc4e473c4e
diff --git a/media/libmediatranscoding/transcoder/PassthroughTrackTranscoder.cpp b/media/libmediatranscoding/transcoder/PassthroughTrackTranscoder.cpp
index 4404bbb..7806208 100644
--- a/media/libmediatranscoding/transcoder/PassthroughTrackTranscoder.cpp
+++ b/media/libmediatranscoding/transcoder/PassthroughTrackTranscoder.cpp
@@ -134,7 +134,7 @@
         }
 
         sample->info = info;
-        if (mOutputQueue.enqueue(sample)) {
+        if (mOutputQueue->enqueue(sample)) {
             LOG(ERROR) << "Output queue aborted";
             return AMEDIA_ERROR_IO;
         }
@@ -153,4 +153,7 @@
     mBufferPool->abort();
 }
 
+std::shared_ptr<AMediaFormat> PassthroughTrackTranscoder::getOutputFormat() const {
+    return mSourceFormat;
+}
 }  // namespace android