Add init() to avoid crash when creating ref in constructor.

This reverts commit 50899fb2696d2bb98a4807a237e124f566293f57.

Bug: 195717690
Fix: 195717690
Test: atest VtsHalTvTunerTargetTest
Change-Id: Icae435f1166e6cf2e2f235979e3d1d37d182d517
diff --git a/tv/tuner/aidl/default/Demux.h b/tv/tuner/aidl/default/Demux.h
index 4cfcaab..4d9b7fe 100644
--- a/tv/tuner/aidl/default/Demux.h
+++ b/tv/tuner/aidl/default/Demux.h
@@ -50,7 +50,7 @@
 
 class Demux : public BnDemux {
   public:
-    Demux(int32_t demuxId, Tuner* tuner);
+    Demux(int32_t demuxId, std::shared_ptr<Tuner> tuner);
     ~Demux();
 
     ::ndk::ScopedAStatus setFrontendDataSource(int32_t in_frontendId) override;
@@ -95,7 +95,7 @@
 
   private:
     // Tuner service
-    Tuner* mTuner;
+    std::shared_ptr<Tuner> mTuner;
 
     // Frontend source
     std::shared_ptr<Frontend> mFrontend;