hdmi_cec: deal with the framework side went away.

Register a death recipient to remove the callback if
the framework side died.

BUG: 67913697
Test: VTS
Change-Id: I51ce5c85c9ec5d1bc90cac72f314647e1075d657
diff --git a/tv/cec/1.0/default/HdmiCec.h b/tv/cec/1.0/default/HdmiCec.h
index 34a3bb0..0133abc 100644
--- a/tv/cec/1.0/default/HdmiCec.h
+++ b/tv/cec/1.0/default/HdmiCec.h
@@ -47,7 +47,7 @@
 using ::android::hardware::hidl_string;
 using ::android::sp;
 
-struct HdmiCec : public IHdmiCec {
+struct HdmiCec : public IHdmiCec, public hidl_death_recipient {
     HdmiCec(hdmi_cec_device_t* device);
     // Methods from ::android::hardware::tv::cec::V1_0::IHdmiCec follow.
     Return<Result> addLogicalAddress(CecLogicalAddress addr)  override;
@@ -87,7 +87,12 @@
         }
     }
 
-private:
+    virtual void serviceDied(uint64_t /*cookie*/,
+                             const wp<::android::hidl::base::V1_0::IBase>& /*who*/) {
+        setCallback(nullptr);
+    }
+
+   private:
     static sp<IHdmiCecCallback> mCallback;
     const hdmi_cec_device_t* mDevice;
 };