Revert "Revert "Audio V4: Send volume and duplicated track attr in update metadata""

The original patch was breaking the fast track volume, so it was
reverted.
In order to fix the original patch, revert the revert and in the
following patch apply the fix.
This makes review easier as only the difference to the original patch
will be present.

Bug: 38184704
Bug: 69623109
Bug: 77892019
Test: Patch already tested for original patch and is tested for following
      patch that fixes this patch.
This reverts commit 80ee2722d64a73777fa76027b1568e61dec8d910.
Change-Id: I06914911c2435df167fff05ce5ca40dd1ed90f39
diff --git a/services/audioflinger/Tracks.cpp b/services/audioflinger/Tracks.cpp
index 236412b..ee9ce84 100644
--- a/services/audioflinger/Tracks.cpp
+++ b/services/audioflinger/Tracks.cpp
@@ -407,6 +407,9 @@
     // mSinkTimestamp
     mFastIndex(-1),
     mCachedVolume(1.0),
+    /* The track might not play immediately after being active, similarly as if its volume was 0.
+     * When the track starts playing, its volume will be computed. */
+    mFinalVolume(0.f),
     mResumeToStopping(false),
     mFlushHwPending(false),
     mFlags(flags)
@@ -997,6 +1000,23 @@
     return mVolumeHandler->getVolumeShaperState(id);
 }
 
+void AudioFlinger::PlaybackThread::Track::setFinalVolume(float volume)
+{
+    if (mFinalVolume != volume) { // Compare to an epsilon if too many meaningless updates
+        mFinalVolume = volume;
+        setMetadataHasChanged();
+    }
+}
+
+void AudioFlinger::PlaybackThread::Track::copyMetadataTo(MetadataInserter& backInserter) const
+{
+    *backInserter++ = {
+            .usage = mAttr.usage,
+            .content_type = mAttr.content_type,
+            .gain = mFinalVolume,
+    };
+}
+
 status_t AudioFlinger::PlaybackThread::Track::getTimestamp(AudioTimestamp& timestamp)
 {
     if (!isOffloaded() && !isDirect()) {
@@ -1427,6 +1447,21 @@
     return outputBufferFull;
 }
 
+void AudioFlinger::PlaybackThread::OutputTrack::copyMetadataTo(MetadataInserter& backInserter) const
+{
+    std::lock_guard<std::mutex> lock(mTrackMetadatasMutex);
+    backInserter = std::copy(mTrackMetadatas.begin(), mTrackMetadatas.end(), backInserter);
+}
+
+void AudioFlinger::PlaybackThread::OutputTrack::setMetadatas(const SourceMetadatas& metadatas) {
+    {
+        std::lock_guard<std::mutex> lock(mTrackMetadatasMutex);
+        mTrackMetadatas = metadatas;
+    }
+    // No need to adjust metadata track volumes as OutputTrack volumes are always 0dBFS.
+    setMetadataHasChanged();
+}
+
 status_t AudioFlinger::PlaybackThread::OutputTrack::obtainBuffer(
         AudioBufferProvider::Buffer* buffer, uint32_t waitTimeMs)
 {