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/tests/PassthroughTrackTranscoderTests.cpp b/media/libmediatranscoding/transcoder/tests/PassthroughTrackTranscoderTests.cpp
index 7a92a37..316793a 100644
--- a/media/libmediatranscoding/transcoder/tests/PassthroughTrackTranscoderTests.cpp
+++ b/media/libmediatranscoding/transcoder/tests/PassthroughTrackTranscoderTests.cpp
@@ -166,7 +166,8 @@
     // Pull transcoder's output samples and compare against input checksums.
     uint64_t sampleCount = 0;
     std::shared_ptr<MediaSample> sample;
-    while (!transcoder.mOutputQueue.dequeue(&sample)) {
+    std::shared_ptr<MediaSampleQueue> outputQueue = transcoder.getOutputQueue();
+    while (!outputQueue->dequeue(&sample)) {
         ASSERT_NE(sample, nullptr);
 
         if (sample->info.flags & SAMPLE_FLAG_END_OF_STREAM) {