Add demux to mFrontendTests

aosp/2640754 adds a tuneFrontend call with testWithDemux enabled.
tuneFrontend() has some logic that calls DvrTests->openDvrInDemux()
which requires mDemux to be available, but mFrontendTests does not
have an associated demux. This CL adds a demux resource.

Bug: 317268814
Test: atest VtsHalTvTunerTargetTest
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:e75c56787a1a9cd6280ab758788bc810ff50cb58)
Merged-In: I3eb69d8dc10cd2cdbb2d3526317faee2909787f5
Change-Id: I3eb69d8dc10cd2cdbb2d3526317faee2909787f5
diff --git a/tv/tuner/aidl/vts/functional/VtsHalTvTunerTargetTest.cpp b/tv/tuner/aidl/vts/functional/VtsHalTvTunerTargetTest.cpp
index 3664b6c..6987588 100644
--- a/tv/tuner/aidl/vts/functional/VtsHalTvTunerTargetTest.cpp
+++ b/tv/tuner/aidl/vts/functional/VtsHalTvTunerTargetTest.cpp
@@ -48,6 +48,7 @@
     ASSERT_TRUE(mFrontendTests.setFrontendCallback());
     ASSERT_TRUE(mDemuxTests.openDemux(demux, demuxId));
     ASSERT_TRUE(mDemuxTests.setDemuxFrontendDataSource(feId));
+    mFrontendTests.setDemux(demux);
     mFilterTests.setDemux(demux);
     ASSERT_TRUE(mFilterTests.openFilterInDemux(filterConf.type, filterConf.bufferSize));
     ASSERT_TRUE(mFilterTests.getNewlyOpenedFilterId_64bit(filterId));