GenericSource: perform seekTo on own looper

Test: pass Media continuous CTS tests
Bug: 69328257
Bug: 66952371
Change-Id: Ia02abbf7a19a01cb6d6051ef9f2461679852dd56
diff --git a/media/libmediaplayerservice/nuplayer/GenericSource.h b/media/libmediaplayerservice/nuplayer/GenericSource.h
index 16c0224..cb9c27f 100644
--- a/media/libmediaplayerservice/nuplayer/GenericSource.h
+++ b/media/libmediaplayerservice/nuplayer/GenericSource.h
@@ -112,6 +112,7 @@
         kWhatSendTimedTextData,
         kWhatChangeAVSource,
         kWhatPollBuffering,
+        kWhatSeek,
         kWhatReadBuffer,
         kWhatStart,
         kWhatResume,
@@ -183,6 +184,9 @@
     void finishPrepareAsync();
     status_t startSources();
 
+    void onSeek(const sp<AMessage>& msg);
+    status_t doSeek(int64_t seekTimeUs, MediaPlayerSeekMode mode);
+
     void onPrepareAsync();
 
     void fetchTextData(