Transcoder: Remove high priority thread from transcoder library.

Use the default thread priority for all transcoder library threads.
Note that this does not impact any codec framework threads.

Bug: 183751395
Test: build_and_run_all_unit_tests.sh
Change-Id: I639085e5cd5a2f379ef852e6cdd7b8a780580c6c
diff --git a/media/libmediatranscoding/transcoder/VideoTrackTranscoder.cpp b/media/libmediatranscoding/transcoder/VideoTrackTranscoder.cpp
index 4405180..383bedd 100644
--- a/media/libmediatranscoding/transcoder/VideoTrackTranscoder.cpp
+++ b/media/libmediatranscoding/transcoder/VideoTrackTranscoder.cpp
@@ -21,7 +21,6 @@
 #include <android-base/properties.h>
 #include <media/NdkCommon.h>
 #include <media/VideoTrackTranscoder.h>
-#include <utils/AndroidThreads.h>
 
 using namespace AMediaFormatUtils;
 
@@ -589,8 +588,6 @@
 }
 
 media_status_t VideoTrackTranscoder::runTranscodeLoop(bool* stopped) {
-    androidSetThreadPriority(0 /* tid (0 = current) */, ANDROID_PRIORITY_VIDEO);
-
     // Push start decoder and encoder as two messages, so that these are subject to the
     // stop request as well. If the session is cancelled (or paused) immediately after start,
     // we don't need to waste time start then stop the codecs.